Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/tabs/tab_strip_controller.mm

+// Copyright 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/ui/tabs/tab_strip_controller.h"
+#import "ios/chrome/browser/ui/tabs/tab_strip_controller_private.h"
+
+#include <cmath>
+#include <vector>
+
+#include "base/i18n/rtl.h"
+#import "base/ios/weak_nsobject.h"
+#include "base/mac/bundle_locations.h"
+#include "base/mac/foundation_util.h"
+#include "base/mac/objc_property_releaser.h"
+#include "base/mac/scoped_nsobject.h"
+#include "base/metrics/user_metrics.h"
+#include "base/metrics/user_metrics_action.h"
+#include "base/strings/sys_string_conversions.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/chrome/browser/experimental_flags.h"
+#import "ios/chrome/browser/tabs/tab.h"
+#import "ios/chrome/browser/tabs/tab_model.h"
+#import "ios/chrome/browser/tabs/tab_model_observer.h"
+#import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
+#include "ios/chrome/browser/ui/commands/ios_command_ids.h"
+#import "ios/chrome/browser/ui/fullscreen_controller.h"
+#include "ios/chrome/browser/ui/rtl_geometry.h"
+#include "ios/chrome/browser/ui/tab_switcher/tab_switcher_tab_strip_placeholder_view.h"
+#import "ios/chrome/browser/ui/tabs/tab_strip_controller+tab_switcher_animation.h"
+#import "ios/chrome/browser/ui/tabs/tab_strip_view.h"
+#import "ios/chrome/browser/ui/tabs/tab_view.h"
+#include "ios/chrome/browser/ui/tabs/target_frame_cache.h"
+#include "ios/chrome/browser/ui/ui_util.h"
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
+#import "ios/chrome/browser/ui/util/snapshot_util.h"
+#include "ios/chrome/grit/ios_strings.h"
+#import "ios/web/public/web_state/web_state.h"
+#include "third_party/google_toolbox_for_mac/src/iPhone/GTMFadeTruncatingLabel.h"
+#include "ui/gfx/image/image.h"
+
+using base::UserMetricsAction;
+
+NSString* const kWillStartTabStripTabAnimation =
+    @"kWillStartTabStripTabAnimation";
+NSString* const kTabStripDragStarted = @"kTabStripDragStarted";
+NSString* const kTabStripDragEnded = @"kTabStripDragEnded";
+
+namespace TabStrip {
+UIColor* BackgroundColor() {
+  DCHECK(IsIPadIdiom());
+  return [UIColor colorWithRed:0.149 green:0.149 blue:0.164 alpha:1];
+}
+}
+
+namespace {
+
+// Animation duration for tab animations.
+const NSTimeInterval kTabAnimationDuration = 0.25;
+
+// Animation duration for tab strip fade.
+const NSTimeInterval kTabStripFadeAnimationDuration = 0.15;
+
+// Amount of time needed to trigger drag and drop mode when long pressing.
+const NSTimeInterval kDragAndDropLongPressDuration = 0.4;
+
+// Tab dimensions.
+const CGFloat kTabOverlap = 26.0;
+const CGFloat kTabOverlapForCompactLayout = 30.0;
+
+const CGFloat kNewTabOverlap = 8.0;
+const CGFloat kMaxTabWidth = 265.0;
+
+// Toggle button dimensions.
+const CGFloat kModeToggleButtonWidth = 36.0;
+const CGFloat kTabSwitcherToggleButtonWidth = 46.0;
+const CGFloat kModeToggleButtonBackgroundWidth = 62.0;
+
+const CGFloat kNewTabRightPadding = 4.0;
+const CGFloat kMinTabWidth = 200.0;
+const CGFloat kMinTabWidthForCompactLayout = 160.0;
+
+const CGFloat kCollapsedTabOverlap = 5.0;
+const NSUInteger kMaxNumCollapsedTabs = 3;
+const NSUInteger kMaxNumCollapsedTabsForCompactLayout = 0;
+
+// Tabs with a visible width smaller than this draw as collapsed tabs..
+const CGFloat kCollapsedTabWidthThreshold = 40.0;
+
+// Autoscroll constants.  The autoscroll distance is set to
+// |kMaxAutoscrollDistance| at the edges of the scroll view.  As the tab moves
+// away from the edges of the scroll view, the autoscroll distance decreases by
+// one for each |kAutoscrollDecrementWidth| points.
+const CGFloat kMaxAutoscrollDistance = 10.0;
+const CGFloat kAutoscrollDecrementWidth = 10.0;
+
+// Dimming view constants, in points.
+const CGFloat kDimmingViewBottomInsetHighRes = 0.0;
+const CGFloat kDimmingViewBottomInset = 0.0;
+
+// The size of the tab strip view.
+const CGFloat kTabStripHeight = 39.0;
+
+// The size of the new tab button.
+const CGFloat kNewTabButtonWidth = 59.9;
+
+// Default image insets for the new tab button.
+const CGFloat kNewTabButtonHorizontalImageInset = 2.0;
+const CGFloat kNewTabButtonTopImageInset = 6.0;
+const CGFloat kNewTabButtonBottomImageInset = 7.0;
+
+// Offsets needed to keep the UI properly centered on high-res screens, in
+// points.
+const CGFloat kNewTabButtonBottomOffsetHighRes = 2.0;
+}
+
+@interface TabStripController ()<TabModelObserver,
+                                 TabStripViewLayoutDelegate,
+                                 UIGestureRecognizerDelegate,
+                                 UIScrollViewDelegate> {
+  base::scoped_nsobject<TabModel> _tabModel;
+  UIView* _view;
+  TabStripView* _tabStripView;
+  UIButton* _buttonNewTab;
+  UIButton* _modeToggleButton;         // weak, nil if not visible.
+  UIButton* _tabSwitcherToggleButton;  // weak, nil if not visible.
+
+  // Background view of the toggle button. Only visible while in compact layout.
+  base::scoped_nsobject<UIImageView> _toggleButtonBackgroundView;
+
+  TabStrip::Style _style;
+  base::WeakNSProtocol<id<FullScreenControllerDelegate>> _fullscreenDelegate;
+
+  // Array of TabViews.  There is a one-to-one correspondence between this array
+  // and the set of Tabs in the TabModel.
+  base::scoped_nsobject<NSMutableArray> _tabArray;
+
+  // Set of TabViews that are currently closing.  These TabViews are also in
+  // |_tabArray|.  Used to translate between |_tabArray| indexes and TabModel
+  // indexes.
+  base::scoped_nsobject<NSMutableSet> _closingTabs;
+
+  // Tracks target frames for TabViews.
+  // TODO(rohitrao): This is unnecessary, as UIKit updates view frames
+  // immediately, so [view frame] will always return the end state of the
+  // current animation.  We can remove this cache entirely.  b/5516053
+  TargetFrameCache _targetFrames;
+
+  // Animate when doing layout.  This flag is set by setNeedsLayoutWithAnimation
+  // and cleared in layoutSubviews.
+  BOOL _animateLayout;
+
+  // The current tab width.  Recomputed whenever a tab is added or removed.
+  CGFloat _currentTabWidth;
+
+  // View used to dim unselected tabs when in reordering mode.  Nil when not
+  // reordering tabs.
+  base::scoped_nsobject<UIView> _dimmingView;
+
+  // Is the selected tab highlighted, used when dragging or swiping tabs.
+  BOOL _highlightsSelectedTab;
+
+  // YES when in reordering mode.
+  // TODO(rohitrao): This is redundant with |_draggedTab|.  Remove it.
+  BOOL _isReordering;
+
+  // The tab that is currently being dragged.  nil when not in reordering mode.
+  base::scoped_nsobject<TabView> _draggedTab;
+
+  // The last known location of the touch that is dragging the tab.  This
+  // location is in the coordinate system of |[_tabStripView superview]| because
+  // that coordinate system does not change as the scroll view scrolls.
+  CGPoint _lastDragLocation;
+
+  // Timer used to autoscroll when in reordering mode.  Is nil when not active.
+  // Owned by its runloop.
+  NSTimer* _autoscrollTimer;  // weak
+
+  // The distance to scroll for each autoscroll timer tick.  If negative, the
+  // tabstrip will scroll to the left; if positive, to the right.
+  CGFloat _autoscrollDistance;
+
+  // The model index of the placeholder gap, if one exists.  This value is used
+  // as the new model index of the dragged tab when it is dropped.
+  NSUInteger _placeholderGapModelIndex;
+
+  // If YES, display the mode toggle switch at the left side of the strip. Can
+  // be set after creation.
+  BOOL _hasModeToggleSwitch;
+
+  // If YES, display the tab switcher toggle switch at the left side of the
+  // strip. Can be set after creation.
+  BOOL _hasTabSwitcherToggleSwitch;
+
+  base::mac::ObjCPropertyReleaser _propertyReleaser_TabStripController;
+}
+
+@property(nonatomic, readonly, retain) TabStripView* tabStripView;
+@property(nonatomic, readonly, retain) UIButton* buttonNewTab;
+@property(nonatomic, readonly, assign) UIButton* tabSwitcherToggleButton;
+
+// Initializes the tab array based on the the entries in the TabModel.  Creates
+// one TabView per Tab and adds it to the tabstrip.  A later call to
+// |-layoutTabs| is needed to properly place the tabs in the correct positions.
+- (void)initializeTabArrayFromTabModel;
+
+// Initializes the tab array to have only one empty tab, for the case (used
+// during startup) when there is not a tab model available.
+- (void)initializeTabArrayWithNoModel;
+
+// Add and remove the mode toggle icon and adjusts the size of the scroll view
+// accordingly. Assumes incognito style has already been checked.
+- (void)installModeToggleButton;
+- (void)removeModeToggleButton;
+
+// Add and remove the tab switcher toggle icon and adjusts the size of the
+// scroll view accordingly. The tab switcher toggle button is replacing the
+// incognito mode toggle button.
+// TODO:(jbbegue) crbug/477676 Remove reference to the incognito toggle button
+// once we know for sure that it will be replaced by the tab switcher toggle
+// button.
+- (void)installTabSwitcherToggleButton;
+- (void)removeTabSwitcherToggleButton;
+
+// Returns an autoreleased TabView object with no content.
+- (TabView*)emptyTabView;
+
+// Returns an autoreleased TabView object based on the given Tab.
+// |isSelected| is passed in here as an optimization, so that the TabView is
+// drawn correctly the first time, without requiring the model to send a
+// -setSelected message to the TabView.
+- (TabView*)tabViewForTab:(Tab*)tab isSelected:(BOOL)isSelected;
+
+// Creates and installs the view used to dim unselected tabs.  Does nothing if
+// the view already exists.
+- (void)installDimmingViewWithAnimation:(BOOL)animate;
+
+// Remove the dimming view,
+- (void)removeDimmingViewWithAnimation:(BOOL)animate;
+
+// Converts between model indexes and |_tabArray| indexes.  The conversion is
+// necessary because |_tabArray| contains closing tabs whereas the TabModel does
+// not.
+- (NSUInteger)indexForModelIndex:(NSUInteger)modelIndex;
+- (NSUInteger)modelIndexForIndex:(NSUInteger)index;
+- (NSUInteger)modelIndexForTabView:(TabView*)view;
+
+// Helper methods to handle each stage of a drag.
+- (void)beginDrag:(UILongPressGestureRecognizer*)gesture;
+- (void)continueDrag:(UILongPressGestureRecognizer*)gesture;
+- (void)endDrag:(UILongPressGestureRecognizer*)gesture;
+- (void)cancelDrag:(UILongPressGestureRecognizer*)gesture;
+
+// Resets any internal variables used to track drag state.
+- (void)resetDragState;
+
+// Returns whether or not the tabstrip is currently in reordering mode.
+- (BOOL)isReorderingTabs;
+
+// Installs or removes the autoscroll timer.
+- (void)installAutoscrollTimerIfNeeded;
+- (void)removeAutoscrollTimer;
+
+// Called once per autoscroll timer tick.  Adjusts the scroll view's content
+// offset as needed.
+- (void)autoscrollTimerFired:(NSTimer*)timer;
+
+// Calculates and stores the autoscroll distance for the given tab view.  The
+// autoscroll distance is a function of the distance between the edge of the
+// scroll view and the tab's frame.
+- (void)computeAutoscrollDistanceForTabView:(TabView*)view;
+
+// Constrains the stored autoscroll distance to prevent the scroll view from
+// overscrolling.
+- (void)constrainAutoscrollDistance;
+
+#if 0
+// Returns the appropriate model index for the currently dragged tab, given its
+// current position.  (If dropped, the tab would be at this index in the model.)
+// TODO(rohitrao): Implement this method.
+- (NSUInteger)modelIndexForDraggedTab;
+#endif
+
+// Returns the horizontal visible tab strip width used to compute the tab width
+// and the tabs and new tab button in regular layout mode.
+// Takes into account whether or not the mode toggle button is showing.
+- (CGFloat)tabStripVisibleSpace;
+
+// Updates the scroll view's content size based on the current set of tabs and
+// closing tabs.  After updating the content size, repositions views so they
+// they will appear stationary on screen.
+- (void)updateContentSizeAndRepositionViews;
+
+// Returns the frame, in the scroll view content's coordinate system, of the
+// given tab view.
+- (CGRect)scrollViewFrameForTab:(TabView*)view;
+
+// Returns the portion of |frame| which is not covered by |frameOnTop|.
+- (CGRect)calculateVisibleFrameForFrame:(CGRect)frame
+                         whenUnderFrame:(CGRect)frameOnTop;
+
+// Schedules a layout of the scroll view and sets the internal |_animateLayout|
+// flag so that the layout will be animated.
+- (void)setNeedsLayoutWithAnimation;
+
+// Returns the maximum number of collapsed tabs depending on the current layout
+// mode.
+- (NSUInteger)maxNumCollapsedTabs;
+
+// Returns the tab overlap width depending on the current layout mode.
+- (CGFloat)tabOverlap;
+
+// Returns the minimum tab view width depending on the current layout mode.
+- (CGFloat)minTabWidth;
+
+// Updates the content offset of the tab strip view in order to keep the
+// selected tab view visible.
+// Content offset adjustement is only needed/performed in compact mode.
+// This method must be called with a valid |tabIndex|.
+- (void)updateContentOffsetForTabIndex:(NSUInteger)tabIndex;
+
+// Update the frame of the tab strip view (scrollview) frame, content inset and
+// toggle buttons states depending on the current layout mode.
+- (void)updateScrollViewFrameForToggleButton;
+
+@end
+
+@implementation TabStripController
+
+@synthesize buttonNewTab = _buttonNewTab;
+@synthesize hasModeToggleSwitch = _hasModeToggleSwitch;
+@synthesize hasTabSwitcherToggleSwitch = _hasTabSwitcherToggleSwitch;
+@synthesize highlightsSelectedTab = _highlightsSelectedTab;
+@synthesize modeToggleButton = _modeToggleButton;
+@synthesize tabStripView = _tabStripView;
+@synthesize tabSwitcherToggleButton = _tabSwitcherToggleButton;
+@synthesize view = _view;
+
+- (instancetype)initWithTabModel:(TabModel*)tabModel
+                           style:(TabStrip::Style)style {
+  if ((self = [super init])) {
+    _propertyReleaser_TabStripController.Init(self, [TabStripController class]);
+    _tabArray.reset([[NSMutableArray alloc] initWithCapacity:10]);
+    _closingTabs.reset([[NSMutableSet alloc] initWithCapacity:5]);
+
+    _tabModel.reset([tabModel retain]);
+    [_tabModel addObserver:self];
+    _style = style;
+    _hasModeToggleSwitch = NO;
+    _hasTabSwitcherToggleSwitch = NO;
+
+    // |self.view| setup.
+    CGRect tabStripFrame = [UIApplication sharedApplication].keyWindow.bounds;
+    tabStripFrame.size.height = kTabStripHeight;
+    _view = [[UIView alloc] initWithFrame:tabStripFrame];
+    _view.autoresizingMask = (UIViewAutoresizingFlexibleWidth |
+                              UIViewAutoresizingFlexibleBottomMargin);
+    _view.backgroundColor = TabStrip::BackgroundColor();
+    if (UseRTLLayout())
+      _view.transform = CGAffineTransformMakeScale(-1, 1);
+
+    // |self.tabStripView| setup.
+    _tabStripView = [[TabStripView alloc] initWithFrame:_view.bounds];
+    _tabStripView.autoresizingMask =
+        (UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight);
+    _tabStripView.backgroundColor = _view.backgroundColor;
+    _tabStripView.layoutDelegate = self;
+    _tabStripView.accessibilityIdentifier = style == TabStrip::kStyleIncognito
+                                                ? @"Incognito Tab Strip"
+                                                : @"Tab Strip";
+    [_view addSubview:_tabStripView];
+
+    // |self.buttonNewTab| setup.
+    CGRect buttonNewTabFrame = tabStripFrame;
+    buttonNewTabFrame.size.width = kNewTabButtonWidth;
+    _buttonNewTab = [[UIButton alloc] initWithFrame:buttonNewTabFrame];
+    BOOL isBrowserStateIncognito =
+        tabModel && tabModel.browserState->IsOffTheRecord();
+    _buttonNewTab.tag =
+        isBrowserStateIncognito ? IDC_NEW_INCOGNITO_TAB : IDC_NEW_TAB;
+    // TODO(crbug.com/600829): Rewrite layout code and convert these masks to
+    // to trailing and leading margins rather than right and bottom.
+    _buttonNewTab.autoresizingMask = (UIViewAutoresizingFlexibleRightMargin |
+                                      UIViewAutoresizingFlexibleBottomMargin);
+    _buttonNewTab.imageView.contentMode = UIViewContentModeCenter;
+    UIImage* buttonNewTabImage = nil;
+    UIImage* buttonNewTabPressedImage = nil;
+    if (_style == TabStrip::kStyleIncognito) {
+      buttonNewTabImage = [UIImage imageNamed:@"tabstrip_new_tab_incognito"];
+      buttonNewTabPressedImage =
+          [UIImage imageNamed:@"tabstrip_new_tab_incognito_pressed"];
+    } else {
+      buttonNewTabImage = [UIImage imageNamed:@"tabstrip_new_tab"];
+      buttonNewTabPressedImage =
+          [UIImage imageNamed:@"tabstrip_new_tab_pressed"];
+    }
+    [_buttonNewTab setImage:buttonNewTabImage forState:UIControlStateNormal];
+    [_buttonNewTab setImage:buttonNewTabPressedImage
+                   forState:UIControlStateHighlighted];
+    UIEdgeInsets imageInsets = UIEdgeInsetsMake(
+        kNewTabButtonTopImageInset, kNewTabButtonHorizontalImageInset,
+        kNewTabButtonBottomImageInset, kNewTabButtonHorizontalImageInset);
+    if (IsHighResScreen()) {
+      imageInsets.top += kNewTabButtonBottomOffsetHighRes;
+      imageInsets.bottom -= kNewTabButtonBottomOffsetHighRes;
+    }
+    _buttonNewTab.imageEdgeInsets = imageInsets;
+    SetA11yLabelAndUiAutomationName(
+        _buttonNewTab,
+        isBrowserStateIncognito ? IDS_IOS_TOOLS_MENU_NEW_INCOGNITO_TAB
+                                : IDS_IOS_TOOLS_MENU_NEW_TAB,
+        isBrowserStateIncognito ? @"New Incognito Tab" : @"New Tab");
+    // Use a nil target to send |-chromeExecuteCommand:| down the responder
+    // chain.
+    [_buttonNewTab addTarget:nil
+                      action:@selector(chromeExecuteCommand:)
+            forControlEvents:UIControlEventTouchUpInside];
+    [_buttonNewTab addTarget:self
+                      action:@selector(recordUserMetrics:)
+            forControlEvents:UIControlEventTouchUpInside];
+    [_tabStripView addSubview:_buttonNewTab];
+
+    // Add tab buttons to tab strip.
+    if (_tabModel)
+      [self initializeTabArrayFromTabModel];
+    else
+      [self initializeTabArrayWithNoModel];
+
+    // Update the layout of the tab buttons.
+    [self updateContentSizeAndRepositionViews];
+    [self layoutTabStripSubviews];
+
+    // Don't highlight the selected tab by default.
+    self.highlightsSelectedTab = NO;
+  }
+  return self;
+}
+
+- (instancetype)init {
+  NOTREACHED();
+  return nil;
+}
+
+- (void)dealloc {
+  [_tabStripView setDelegate:nil];
+  [_tabStripView setLayoutDelegate:nil];
+  [_tabModel removeObserver:self];
+  [super dealloc];
+}
+
+- (id<FullScreenControllerDelegate>)fullscreenDelegate {
+  return _fullscreenDelegate;
+}
+
+- (void)setFullscreenDelegate:
+    (id<FullScreenControllerDelegate>)fullscreenDelegate {
+  _fullscreenDelegate.reset(fullscreenDelegate);
+}
+
+- (void)initializeTabArrayFromTabModel {
+  DCHECK(_tabModel);
+  for (Tab* tab in _tabModel.get()) {
+    BOOL isSelectedTab = [_tabModel currentTab] == tab;
+    TabView* view = [self tabViewForTab:tab isSelected:isSelectedTab];
+    [_tabArray addObject:view];
+    [_tabStripView addSubview:view];
+  }
+}
+
+- (void)initializeTabArrayWithNoModel {
+  DCHECK(!_tabModel);
+  TabView* view = [self emptyTabView];
+  [_tabArray addObject:view];
+  [_tabStripView addSubview:view];
+  [view setSelected:YES];
+  return;
+}
+
+- (void)setHasModeToggleSwitch:(BOOL)hasModeToggleSwitch {
+  if (_hasModeToggleSwitch && !hasModeToggleSwitch)
+    [self removeModeToggleButton];
+  if (!_hasModeToggleSwitch && hasModeToggleSwitch)
+    [self installModeToggleButton];
+  if (_hasModeToggleSwitch != hasModeToggleSwitch) {
+    _hasModeToggleSwitch = hasModeToggleSwitch;
+    [self updateContentSizeAndRepositionViews];
+    [self setNeedsLayoutWithAnimation];
+  }
+}
+
+- (void)setHasTabSwitcherToggleSwitch:(BOOL)hasTabSwitcherToggleSwitch {
+  if (_hasTabSwitcherToggleSwitch && !hasTabSwitcherToggleSwitch)
+    [self removeTabSwitcherToggleButton];
+  if (!_hasTabSwitcherToggleSwitch && hasTabSwitcherToggleSwitch)
+    [self installTabSwitcherToggleButton];
+  if (_hasTabSwitcherToggleSwitch != hasTabSwitcherToggleSwitch) {
+    _hasTabSwitcherToggleSwitch = hasTabSwitcherToggleSwitch;
+    [self updateContentSizeAndRepositionViews];
+    [self setNeedsLayoutWithAnimation];
+  }
+}
+
+- (TabView*)emptyTabView {
+  TabView* view =
+      [[[TabView alloc] initWithEmptyView:YES selected:YES] autorelease];
+  [view setIncognitoStyle:(_style == TabStrip::kStyleIncognito)];
+  [view setContentMode:UIViewContentModeRedraw];
+
+  // Setting the tab to be hidden marks it as a new tab.  The layout code will
+  // make the tab visible and set up the appropriate animations.
+  [view setHidden:YES];
+
+  return view;
+}
+
+- (TabView*)tabViewForTab:(Tab*)tab isSelected:(BOOL)isSelected {
+  TabView* view =
+      [[[TabView alloc] initWithEmptyView:NO selected:isSelected] autorelease];
+  if (UseRTLLayout())
+    [view setTransform:CGAffineTransformMakeScale(-1, 1)];
+  [view setIncognitoStyle:(_style == TabStrip::kStyleIncognito)];
+  [view setContentMode:UIViewContentModeRedraw];
+  [[view titleLabel] setText:[tab title]];
+  [view setFavicon:[tab favicon]];
+
+  // Set the tab buttons' action messages.
+  [view addTarget:self
+                action:@selector(tabTapped:)
+      forControlEvents:UIControlEventTouchUpInside];
+  [[view closeButton] addTarget:self
+                         action:@selector(closeTab:)
+               forControlEvents:UIControlEventTouchUpInside];
+
+  // Install a long press gesture recognizer to handle drag and drop.
+  base::scoped_nsobject<UILongPressGestureRecognizer> longPress(
+      [[UILongPressGestureRecognizer alloc]
+          initWithTarget:self
+                  action:@selector(handleLongPress:)]);
+  [longPress setMinimumPressDuration:kDragAndDropLongPressDuration];
+  [longPress setDelegate:self];
+  [view addGestureRecognizer:longPress];
+
+  // Giving the tab view exclusive touch prevents other views from receiving
+  // touches while a TabView is handling a touch.
+  [view setExclusiveTouch:YES];
+
+  // Setting the tab to be hidden marks it as a new tab.  The layout code will
+  // make the tab visible and set up the appropriate animations.
+  [view setHidden:YES];
+
+  return view;
+}
+
+- (void)setHighlightsSelectedTab:(BOOL)highlightsSelectedTab {
+  if (highlightsSelectedTab)
+    [self installDimmingViewWithAnimation:YES];
+  else
+    [self removeDimmingViewWithAnimation:YES];
+
+  _highlightsSelectedTab = highlightsSelectedTab;
+}
+
+- (void)installDimmingViewWithAnimation:(BOOL)animate {
+  // The dimming view should not cover the bottom 2px of the tab strip, as those
+  // pixels are visually part of the top border of the toolbar.  The bottom
+  // inset constants take into account the conversion from pixels to points.
+  CGRect frame = [_tabStripView bounds];
+  frame.size.height -= (IsHighResScreen() ? kDimmingViewBottomInsetHighRes
+                                          : kDimmingViewBottomInset);
+
+  // Create the dimming view if it doesn't exist.  In all cases, make sure it's
+  // set up correctly.
+  if (_dimmingView.get())
+    [_dimmingView setFrame:frame];
+  else
+    _dimmingView.reset([[UIView alloc] initWithFrame:frame]);
+
+  // Enable user interaction in order to eat touches from views behind it.
+  [_dimmingView setUserInteractionEnabled:YES];
+  [_dimmingView setBackgroundColor:[TabStrip::BackgroundColor()
+                                       colorWithAlphaComponent:0]];
+  [_dimmingView setAutoresizingMask:(UIViewAutoresizingFlexibleWidth |
+                                     UIViewAutoresizingFlexibleHeight)];
+  [_tabStripView addSubview:_dimmingView];
+
+  CGFloat duration = animate ? kTabStripFadeAnimationDuration : 0;
+  [UIView animateWithDuration:duration
+                   animations:^{
+                     [_dimmingView
+                         setBackgroundColor:[TabStrip::BackgroundColor()
+                                                colorWithAlphaComponent:0.6]];
+                   }];
+}
+
+- (void)removeDimmingViewWithAnimation:(BOOL)animate {
+  if (_dimmingView) {
+    CGFloat duration = animate ? kTabStripFadeAnimationDuration : 0;
+    [UIView animateWithDuration:duration
+        animations:^{
+          [_dimmingView setBackgroundColor:[TabStrip::BackgroundColor()
+                                               colorWithAlphaComponent:0]];
+        }
+        completion:^(BOOL finished) {
+          // Do not remove the dimming view if the animation was aborted.
+          if (finished) {
+            [_dimmingView removeFromSuperview];
+            _dimmingView.reset();
+          }
+        }];
+  }
+}
+
+- (void)recordUserMetrics:(id)sender {
+  if (sender == _buttonNewTab)
+    base::RecordAction(UserMetricsAction("MobileTabStripNewTab"));
+  else if (sender == _modeToggleButton)
+    base::RecordAction(UserMetricsAction("MobileTabStripSwitchMode"));
+  else if (sender == _tabSwitcherToggleButton)
+    base::RecordAction(UserMetricsAction("MobileTabSwitcherOpen"));
+  else
+    LOG(WARNING) << "Trying to record metrics for unknown sender "
+                 << base::SysNSStringToUTF8([sender description]);
+}
+
+- (void)tabTapped:(id)sender {
+  DCHECK([sender isKindOfClass:[TabView class]]);
+
+  // Ignore taps while in reordering mode.
+  if ([self isReorderingTabs])
+    return;
+
+  NSUInteger index = [self modelIndexForTabView:(TabView*)sender];
+  DCHECK_NE(NSNotFound, static_cast<NSInteger>(index));
+  if (index == NSNotFound)
+    return;
+  Tab* tappedTab = [_tabModel tabAtIndex:index];
+  Tab* currentTab = [_tabModel currentTab];
+  if (IsIPadIdiom() && (currentTab != tappedTab)) {
+    [currentTab updateSnapshotWithOverlay:YES visibleFrameOnly:YES];
+  }
+  [_tabModel setCurrentTab:tappedTab];
+  [self updateContentOffsetForTabIndex:index];
+}
+
+- (void)closeTab:(id)sender {
+  // Ignore taps while in reordering mode.
+  // TODO(rohitrao): We should just hide the close buttons instead.
+  if ([self isReorderingTabs])
+    return;
+
+  base::RecordAction(UserMetricsAction("MobileTabStripCloseTab"));
+  DCHECK([sender isKindOfClass:[UIButton class]]);
+  UIView* superview = [sender superview];
+  DCHECK([superview isKindOfClass:[TabView class]]);
+  TabView* tab = (TabView*)superview;
+  NSUInteger modelIndex = [self modelIndexForTabView:tab];
+  if (modelIndex != NSNotFound)
+    [_tabModel closeTabAtIndex:modelIndex];
+}
+
+- (void)handleLongPress:(UILongPressGestureRecognizer*)gesture {
+  switch ([gesture state]) {
+    case UIGestureRecognizerStateBegan:
+      [[NSNotificationCenter defaultCenter]
+          postNotificationName:kTabStripDragStarted
+                        object:nil];
+      [self beginDrag:gesture];
+      break;
+    case UIGestureRecognizerStateChanged:
+      [self continueDrag:gesture];
+      break;
+    case UIGestureRecognizerStateEnded:
+      [self endDrag:gesture];
+      [[NSNotificationCenter defaultCenter]
+          postNotificationName:kTabStripDragEnded
+                        object:nil];
+      break;
+    case UIGestureRecognizerStateCancelled:
+      [self cancelDrag:gesture];
+      [[NSNotificationCenter defaultCenter]
+          postNotificationName:kTabStripDragEnded
+                        object:nil];
+      break;
+    default:
+      NOTREACHED();
+  }
+}
+
+- (NSUInteger)indexForModelIndex:(NSUInteger)modelIndex {
+  NSUInteger index = modelIndex;
+  NSUInteger i = 0;
+  for (TabView* tab in _tabArray.get()) {
+    if ([_closingTabs containsObject:tab])
+      ++index;
+
+    if (i == index)
+      break;
+
+    ++i;
+  }
+
+  DCHECK_GE(index, modelIndex);
+  return index;
+}
+
+- (NSUInteger)modelIndexForIndex:(NSUInteger)index {
+  NSUInteger modelIndex = 0;
+  NSUInteger arrayIndex = 0;
+  for (TabView* tab in _tabArray.get()) {
+    if (arrayIndex == index) {
+      if ([_closingTabs containsObject:tab])
+        return NSNotFound;
+      return modelIndex;
+    }
+
+    if (![_closingTabs containsObject:tab])
+      ++modelIndex;
+
+    ++arrayIndex;
+  }
+
+  return NSNotFound;
+}
+
+- (NSUInteger)modelIndexForTabView:(TabView*)view {
+  return [self modelIndexForIndex:[_tabArray indexOfObject:view]];
+}
+
+#pragma mark -
+#pragma mark Tab Drag and Drop methods
+
+- (void)beginDrag:(UILongPressGestureRecognizer*)gesture {
+  DCHECK([[gesture view] isKindOfClass:[TabView class]]);
+  TabView* view = (TabView*)[gesture view];
+
+  // Sanity checks.
+  NSUInteger index = [self modelIndexForTabView:view];
+  DCHECK_NE(NSNotFound, static_cast<NSInteger>(index));
+  if (index == NSNotFound)
+    return;
+
+  // Install the dimming view, hide the new tab button, and select the tab so it
+  // appears highlighted.
+  Tab* tab = [_tabModel tabAtIndex:index];
+  self.highlightsSelectedTab = YES;
+  _buttonNewTab.hidden = YES;
+  [_tabModel setCurrentTab:tab];
+
+  // Set up initial drag state.
+  _lastDragLocation = [gesture locationInView:[_tabStripView superview]];
+  _isReordering = YES;
+  _draggedTab.reset([view retain]);
+  _placeholderGapModelIndex = [self modelIndexForTabView:_draggedTab];
+
+  // Update the autoscroll distance and timer.
+  [self computeAutoscrollDistanceForTabView:_draggedTab];
+  if (_autoscrollDistance != 0)
+    [self installAutoscrollTimerIfNeeded];
+  else
+    [self removeAutoscrollTimer];
+}
+
+- (void)continueDrag:(UILongPressGestureRecognizer*)gesture {
+  DCHECK([[gesture view] isKindOfClass:[TabView class]]);
+  TabView* view = (TabView*)[gesture view];
+
+  // Update the position of the dragged tab.
+  CGPoint location = [gesture locationInView:[_tabStripView superview]];
+  CGFloat dx = location.x - _lastDragLocation.x;
+  CGRect frame = [view frame];
+  frame.origin.x += dx;
+  [view setFrame:frame];
+  _lastDragLocation = location;
+
+  // Update the autoscroll distance and timer.
+  [self computeAutoscrollDistanceForTabView:_draggedTab];
+  if (_autoscrollDistance != 0)
+    [self installAutoscrollTimerIfNeeded];
+  else
+    [self removeAutoscrollTimer];
+
+  [self setNeedsLayoutWithAnimation];
+}
+
+- (void)endDrag:(UILongPressGestureRecognizer*)gesture {
+  DCHECK([[gesture view] isKindOfClass:[TabView class]]);
+
+  NSUInteger fromIndex = [self modelIndexForTabView:_draggedTab];
+  // TODO(rohitrao): We're seeing crashes where fromIndex is NSNotFound,
+  // indicating that the dragged tab is no longer in the TabModel.  This could
+  // happen if a tab closed itself during a drag.  Investigate this further, but
+  // for now, simply test |fromIndex| before proceeding.
+  if (fromIndex == NSNotFound) {
+    [self resetDragState];
+    [self setNeedsLayoutWithAnimation];
+    return;
+  }
+
+  Tab* tab = [_tabModel tabAtIndex:fromIndex];
+  NSUInteger toIndex = _placeholderGapModelIndex;
+  DCHECK_NE(NSNotFound, static_cast<NSInteger>(toIndex));
+  DCHECK_LT(toIndex, [_tabModel count]);
+
+  // Reset drag state variables before notifying the model that the tab moved.
+  [self resetDragState];
+
+  [_tabModel moveTab:tab toIndex:toIndex];
+  [self setNeedsLayoutWithAnimation];
+}
+
+- (void)cancelDrag:(UILongPressGestureRecognizer*)gesture {
+  DCHECK([[gesture view] isKindOfClass:[TabView class]]);
+
+  // Reset drag state and trigger a relayout to moved tabs back into their
+  // correct positions.
+  [self resetDragState];
+  [self setNeedsLayoutWithAnimation];
+}
+
+- (void)resetDragState {
+  self.highlightsSelectedTab = NO;
+  _buttonNewTab.hidden = NO;
+  [self removeAutoscrollTimer];
+
+  _isReordering = NO;
+  _placeholderGapModelIndex = NSNotFound;
+  _draggedTab.reset();
+}
+
+- (BOOL)isReorderingTabs {
+  return _isReordering;
+}
+
+- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer*)recognizer {
+  DCHECK([recognizer isKindOfClass:[UILongPressGestureRecognizer class]]);
+
+  // If a drag is already in progress, do not allow another to start.
+  return ![self isReorderingTabs];
+}
+
+#pragma mark -
+#pragma mark Autoscroll methods
+
+- (void)installAutoscrollTimerIfNeeded {
+  if (_autoscrollTimer)
+    return;
+
+  _autoscrollTimer =
+      [NSTimer scheduledTimerWithTimeInterval:(1.0 / 60.0)
+                                       target:self
+                                     selector:@selector(autoscrollTimerFired:)
+                                     userInfo:nil
+                                      repeats:YES];
+}
+
+- (void)removeAutoscrollTimer {
+  [_autoscrollTimer invalidate];
+  _autoscrollTimer = nil;
+}
+
+- (void)autoscrollTimerFired:(NSTimer*)timer {
+  [self constrainAutoscrollDistance];
+
+  CGPoint offset = [_tabStripView contentOffset];
+  offset.x += _autoscrollDistance;
+  [_tabStripView setContentOffset:offset];
+
+  // Fixed-position views need to have their frames adusted to compensate for
+  // the content offset shift.  These include the dragged tab, the dimming
+  // view, and the new tab button.
+  CGRect tabFrame = [_draggedTab frame];
+  tabFrame.origin.x += _autoscrollDistance;
+  [_draggedTab setFrame:tabFrame];
+
+  CGRect dimFrame = [_dimmingView frame];
+  dimFrame.origin.x += _autoscrollDistance;
+  [_dimmingView setFrame:dimFrame];
+
+  // Even though the new tab button is hidden during drag and drop, keep its
+  // frame updated to prevent it from animating back into place when the drag
+  // finishes.
+  CGRect newTabFrame = [_buttonNewTab frame];
+  newTabFrame.origin.x += _autoscrollDistance;
+  [_buttonNewTab setFrame:newTabFrame];
+
+  // TODO(rohitrao): Find a good way to re-enable the sliding over animation
+  // when autoscrolling.  Right now any running animations are immediately
+  // stopped by the next call to autoscrollTimerFired.
+  [_tabStripView setNeedsLayout];
+}
+
+- (void)computeAutoscrollDistanceForTabView:(TabView*)view {
+  CGRect scrollBounds = [_tabStripView bounds];
+  CGRect viewFrame = [view frame];
+
+  // The distance between this tab and the edge of the scroll view.
+  CGFloat distanceFromEdge =
+      MIN(CGRectGetMinX(viewFrame) - CGRectGetMinX(scrollBounds),
+          CGRectGetMaxX(scrollBounds) - CGRectGetMaxX(viewFrame));
+  if (distanceFromEdge < 0)
+    distanceFromEdge = 0;
+
+  // Negative if the tab is closer to the left edge of the scroll view, positive
+  // if it is closer to the right edge.
+  CGFloat leftRightMultiplier =
+      (CGRectGetMidX(viewFrame) < CGRectGetMidX(scrollBounds)) ? -1.0 : 1.0;
+
+  // The autoscroll distance decreases linearly as the tab view gets further
+  // from the edge of the scroll view.
+  _autoscrollDistance =
+      leftRightMultiplier *
+      MAX(0.0, ceilf(kMaxAutoscrollDistance -
+                     distanceFromEdge / kAutoscrollDecrementWidth));
+}
+
+- (void)constrainAutoscrollDistance {
+  // Make sure autoscroll distance is not so large as to cause overscroll.
+  CGPoint offset = [_tabStripView contentOffset];
+
+  // Check to make sure there is no overscroll off the right edge.
+  CGFloat maxOffset = [_tabStripView contentSize].width -
+                      CGRectGetWidth([_tabStripView bounds]);
+  if (offset.x + _autoscrollDistance > maxOffset)
+    _autoscrollDistance = (maxOffset - offset.x);
+
+  // Perform the left edge check after the right edge check, to prevent
+  // right-justifying the tabs when there is no overflow.
+  if (offset.x + _autoscrollDistance < 0)
+    _autoscrollDistance = -offset.x;
+}
+
+#pragma mark -
+#pragma mark TabStripModelObserver methods
+
+// Observer method.
+- (void)tabModel:(TabModel*)model
+    didInsertTab:(Tab*)tab
+         atIndex:(NSUInteger)modelIndex
+    inForeground:(BOOL)fg {
+  TabView* view = [self tabViewForTab:tab isSelected:fg];
+  [_tabArray insertObject:view atIndex:[self indexForModelIndex:modelIndex]];
+  [[self tabStripView] addSubview:view];
+
+  [self updateContentSizeAndRepositionViews];
+  [self setNeedsLayoutWithAnimation];
+  [self updateContentOffsetForTabIndex:modelIndex];
+}
+
+// Observer method.
+- (void)tabModel:(TabModel*)model
+    didRemoveTab:(Tab*)tab
+         atIndex:(NSUInteger)modelIndex {
+  // Keep the actual view around while it is animating out.  Once the animation
+  // is done, remove the view.
+  NSUInteger index = [self indexForModelIndex:modelIndex];
+  TabView* view = [_tabArray objectAtIndex:index];
+  [_closingTabs addObject:view];
+  _targetFrames.RemoveFrame(view);
+
+  // Adjust the content size now that the tab has been removed from the model.
+  [self updateContentSizeAndRepositionViews];
+
+  // Signal the FullscreenController that the toolbar needs to stay on
+  // screen for a bit, so the animation is visible.
+  [[NSNotificationCenter defaultCenter]
+      postNotificationName:kWillStartTabStripTabAnimation
+                    object:nil];
+
+  // Leave the view where it is horizontally and animate it downwards out of
+  // sight.
+  CGRect frame = [view frame];
+  frame = CGRectOffset(frame, 0, CGRectGetHeight(frame));
+  [UIView animateWithDuration:kTabAnimationDuration
+      animations:^{
+        [view setFrame:frame];
+      }
+      completion:^(BOOL finished) {
+        [view removeFromSuperview];
+        [_tabArray removeObject:view];
+        [_closingTabs removeObject:view];
+      }];
+
+  [self setNeedsLayoutWithAnimation];
+}
+
+// Observer method.
+- (void)tabModel:(TabModel*)model
+      didMoveTab:(Tab*)tab
+       fromIndex:(NSUInteger)fromIndex
+         toIndex:(NSUInteger)toIndex {
+  DCHECK(!_isReordering);
+
+  // Reorder the objects in _tabArray to keep in sync with the model ordering.
+  NSUInteger arrayIndex = [self indexForModelIndex:fromIndex];
+  base::scoped_nsobject<TabView> view(
+      [[_tabArray objectAtIndex:arrayIndex] retain]);
+  [_tabArray removeObject:view];
+  [_tabArray insertObject:view atIndex:toIndex];
+  [self setNeedsLayoutWithAnimation];
+}
+
+// Observer method.
+- (void)tabModel:(TabModel*)model
+    didChangeActiveTab:(Tab*)newTab
+           previousTab:(Tab*)previousTab
+               atIndex:(NSUInteger)modelIndex {
+  for (TabView* view in _tabArray.get()) {
+    [view setSelected:NO];
+  }
+
+  NSUInteger index = [self indexForModelIndex:modelIndex];
+  TabView* activeView = [_tabArray objectAtIndex:index];
+  [activeView setSelected:YES];
+
+  // No need to animate this change, as selecting a new tab simply changes the
+  // z-ordering of the TabViews.  If a new tab was selected as a result of a tab
+  // closure, then the animated layout has already been scheduled.
+  [_tabStripView setNeedsLayout];
+}
+
+// Observer method.
+- (void)tabModel:(TabModel*)model didChangeTab:(Tab*)tab {
+  NSUInteger modelIndex = [_tabModel indexOfTab:tab];
+  if (modelIndex == NSNotFound) {
+    DCHECK(false) << "Received notification for a Tab that is not contained in "
+                  << "the TabModel";
+    return;
+  }
+  NSUInteger index = [self indexForModelIndex:modelIndex];
+  TabView* view = [_tabArray objectAtIndex:index];
+  [view setTitle:tab.title];
+  [view setFavicon:[tab favicon]];
+  if (tab.webState->IsLoading())
+    [view startProgressSpinner];
+  else
+    [view stopProgressSpinner];
+  [view setNeedsDisplay];
+}
+
+// Observer method.
+- (void)tabModel:(TabModel*)model
+    didReplaceTab:(Tab*)oldTab
+          withTab:(Tab*)newTab
+          atIndex:(NSUInteger)index {
+  // TabViews do not hold references to their parent Tabs, so it's safe to treat
+  // this as a tab change rather than a tab replace.
+  [self tabModel:model didChangeTab:newTab];
+}
+
+#pragma mark -
+#pragma mark Views and Layout
+
+- (void)installModeToggleButton {
+  // Add the mode toggle button view.
+  DCHECK(!_modeToggleButton);
+  UIImage* toggleIcon = nil;
+  int toggleIdsAccessibilityLabel;
+  NSString* toggleEnglishUiAutomationName;
+  if (_style == TabStrip::kStyleDark) {
+    toggleIcon = [UIImage imageNamed:@"tabstrip_switch"];
+    toggleIdsAccessibilityLabel = IDS_IOS_SWITCH_BROWSER_MODE_ENTER_INCOGNITO;
+    toggleEnglishUiAutomationName = @"Enter Incognito* Mode";
+  } else {
+    toggleIcon = [UIImage imageNamed:@"tabstrip_incognito_switch"];
+    toggleIdsAccessibilityLabel = IDS_IOS_SWITCH_BROWSER_MODE_LEAVE_INCOGNITO;
+    toggleEnglishUiAutomationName = @"Leave Incognito* Mode";
+  }
+  const CGFloat tabStripHeight = _view.frame.size.height;
+  CGRect buttonFrame =
+      CGRectMake(CGRectGetMaxX(_view.frame) - kModeToggleButtonWidth, 0.0,
+                 kModeToggleButtonWidth, tabStripHeight);
+  _modeToggleButton = [UIButton buttonWithType:UIButtonTypeCustom];
+  _modeToggleButton.frame = buttonFrame;
+  [_modeToggleButton setImageEdgeInsets:UIEdgeInsetsMake(7, 5, 7, 5)];
+  _modeToggleButton.autoresizingMask = UIViewAutoresizingFlexibleLeftMargin;
+  _modeToggleButton.backgroundColor = [UIColor clearColor];
+  [_modeToggleButton setImage:toggleIcon forState:UIControlStateNormal];
+  // Set target/action to bubble up with command id as tag.
+  [_modeToggleButton addTarget:nil
+                        action:@selector(chromeExecuteCommand:)
+              forControlEvents:UIControlEventTouchUpInside];
+  [_modeToggleButton setTag:IDC_SWITCH_BROWSER_MODES];
+  [_modeToggleButton addTarget:self
+                        action:@selector(recordUserMetrics:)
+              forControlEvents:UIControlEventTouchUpInside];
+
+  SetA11yLabelAndUiAutomationName(_modeToggleButton,
+                                  toggleIdsAccessibilityLabel,
+                                  toggleEnglishUiAutomationName);
+  [_view addSubview:_modeToggleButton];
+  // Shrink the scroll view.
+  [self updateScrollViewFrameForToggleButton];
+}
+
+- (void)removeModeToggleButton {
+  // Remove the button view.
+  DCHECK(_modeToggleButton);
+  [_modeToggleButton removeFromSuperview];
+  _modeToggleButton = nil;
+  // Extend the scroll view.
+  [self updateScrollViewFrameForToggleButton];
+}
+
+- (CGFloat)tabStripVisibleSpace {
+  CGFloat availableSpace = CGRectGetWidth([_tabStripView bounds]) -
+                           CGRectGetWidth([_buttonNewTab frame]) +
+                           kNewTabOverlap;
+  if (IsCompactTablet()) {
+    if ([self hasModeToggleSwitch])
+      availableSpace -= kNewTabRightPadding + kModeToggleButtonWidth;
+    else
+      availableSpace -= kNewTabRightPadding;
+  } else {
+    if (![self hasModeToggleSwitch])
+      availableSpace -= kNewTabRightPadding;
+  }
+  return availableSpace;
+}
+
+- (void)installTabSwitcherToggleButton {
+  // Add the mode toggle button view.
+  DCHECK(!_tabSwitcherToggleButton);
+  UIImage* tabSwitcherToggleIcon =
+      [UIImage imageNamed:@"tabswitcher_tab_switcher_button"];
+  tabSwitcherToggleIcon = [tabSwitcherToggleIcon
+      imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
+  int tabSwitcherToggleIdsAccessibilityLabel =
+      IDS_IOS_TAB_STRIP_ENTER_TAB_SWITCHER;
+  NSString* tabSwitcherToggleEnglishUiAutomationName = @"Enter Tab Switcher";
+  const CGFloat tabStripHeight = _view.frame.size.height;
+  CGRect buttonFrame =
+      CGRectMake(CGRectGetMaxX(_view.frame) - kTabSwitcherToggleButtonWidth,
+                 0.0, kTabSwitcherToggleButtonWidth, tabStripHeight);
+  _tabSwitcherToggleButton = [UIButton buttonWithType:UIButtonTypeCustom];
+  [_tabSwitcherToggleButton setTintColor:[UIColor whiteColor]];
+  _tabSwitcherToggleButton.frame = buttonFrame;
+  [_tabSwitcherToggleButton setContentMode:UIViewContentModeCenter];
+  _tabSwitcherToggleButton.autoresizingMask =
+      UIViewAutoresizingFlexibleLeftMargin;
+  _tabSwitcherToggleButton.backgroundColor = [UIColor clearColor];
+  _tabSwitcherToggleButton.exclusiveTouch = YES;
+  [_tabSwitcherToggleButton setImage:tabSwitcherToggleIcon
+                            forState:UIControlStateNormal];
+  // Set target/action to bubble up with command id as tag.
+  [_tabSwitcherToggleButton addTarget:nil
+                               action:@selector(chromeExecuteCommand:)
+                     forControlEvents:UIControlEventTouchUpInside];
+  [_tabSwitcherToggleButton setTag:IDC_TOGGLE_TAB_SWITCHER];
+  [_tabSwitcherToggleButton addTarget:self
+                               action:@selector(recordUserMetrics:)
+                     forControlEvents:UIControlEventTouchUpInside];
+
+  SetA11yLabelAndUiAutomationName(_tabSwitcherToggleButton,
+                                  tabSwitcherToggleIdsAccessibilityLabel,
+                                  tabSwitcherToggleEnglishUiAutomationName);
+  [_view addSubview:_tabSwitcherToggleButton];
+  // Shrink the scroll view.
+  [self updateScrollViewFrameForToggleButton];
+}
+
+- (void)removeTabSwitcherToggleButton {
+  // Remove the button view.
+  DCHECK(_tabSwitcherToggleButton);
+  [_tabSwitcherToggleButton removeFromSuperview];
+  _tabSwitcherToggleButton = nil;
+  // Extend the scroll view.
+  [self updateScrollViewFrameForToggleButton];
+}
+
+- (void)updateContentSizeAndRepositionViews {
+  // TODO(rohitrao): The following lines are duplicated in
+  // layoutTabStripSubviews.  Find a way to consolidate this logic.
+  const NSUInteger tabCount = [_tabArray count] - [_closingTabs count];
+  if (!tabCount)
+    return;
+  const CGFloat tabHeight = CGRectGetHeight([_tabStripView bounds]);
+  CGFloat visibleSpace = [self tabStripVisibleSpace];
+  _currentTabWidth =
+      (visibleSpace + ([self tabOverlap] * (tabCount - 1))) / tabCount;
+  _currentTabWidth = MIN(_currentTabWidth, kMaxTabWidth);
+  _currentTabWidth = MAX(_currentTabWidth, [self minTabWidth]);
+
+  // Set the content size to be large enough to contain all the tabs at the
+  // desired width, with the standard overlap, plus the new tab button.
+  CGSize contentSize = CGSizeMake(
+      _currentTabWidth * tabCount - ([self tabOverlap] * (tabCount - 1)) +
+          CGRectGetWidth([_buttonNewTab frame]) - kNewTabOverlap,
+      tabHeight);
+  if (CGSizeEqualToSize([_tabStripView contentSize], contentSize))
+    return;
+
+  // Background: The scroll view might change the content offset when updating
+  // the content size.  This can happen when the old content offset would result
+  // in an overscroll at the new content size.  (Note that the content offset
+  // will never change if the content size is growing.)
+  //
+  // To handle this without making views appear to jump, shift all of the
+  // subviews by an amount equal to the size change.  This effectively places
+  // the subviews back where they were before the change, in terms of screen
+  // coordinates.
+  CGPoint oldOffset = [_tabStripView contentOffset];
+  [_tabStripView setContentSize:contentSize];
+
+  CGFloat dx = [_tabStripView contentOffset].x - oldOffset.x;
+  for (UIView* view in [_tabStripView subviews]) {
+    CGRect frame = [view frame];
+    frame.origin.x += dx;
+    [view setFrame:frame];
+    _targetFrames.AddFrame(view, frame);
+  }
+}
+
+- (CGRect)scrollViewFrameForTab:(TabView*)view {
+  NSUInteger index = [self modelIndexForTabView:view];
+
+  CGRect frame = [view frame];
+  frame.origin.x =
+      (_currentTabWidth * index) - ([self tabOverlap] * (index - 1));
+  return frame;
+}
+
+- (CGRect)calculateVisibleFrameForFrame:(CGRect)frame
+                         whenUnderFrame:(CGRect)frameOnTop {
+  CGFloat minX = CGRectGetMinX(frame);
+  CGFloat maxX = CGRectGetMaxX(frame);
+
+  if (CGRectGetMinX(frame) < CGRectGetMinX(frameOnTop))
+    maxX = CGRectGetMinX(frameOnTop);
+  else
+    minX = CGRectGetMaxX(frameOnTop);
+
+  frame.origin.x = minX;
+  frame.size.width = maxX - minX;
+  return frame;
+}
+
+#pragma mark -
+#pragma mark - compact layout
+
+- (NSUInteger)maxNumCollapsedTabs {
+  return IsCompactTablet() ? kMaxNumCollapsedTabsForCompactLayout
+                           : kMaxNumCollapsedTabs;
+}
+
+- (CGFloat)tabOverlap {
+  return IsCompactTablet() ? kTabOverlapForCompactLayout : kTabOverlap;
+}
+
+- (CGFloat)minTabWidth {
+  return IsCompactTablet() ? kMinTabWidthForCompactLayout : kMinTabWidth;
+}
+
+- (void)updateContentOffsetForTabIndex:(NSUInteger)tabIndex {
+  DCHECK_NE(NSNotFound, static_cast<NSInteger>(tabIndex));
+
+  if (IsCompactTablet()) {
+    if (tabIndex == [_tabArray count] - 1) {
+      const CGFloat tabStripAvailableSpace =
+          _tabStripView.frame.size.width - _tabStripView.contentInset.right;
+      if (_tabStripView.contentSize.width > tabStripAvailableSpace) {
+        CGFloat scrollToPoint =
+            _tabStripView.contentSize.width - tabStripAvailableSpace;
+        [_tabStripView setContentOffset:CGPointMake(scrollToPoint, 0)
+                               animated:YES];
+      }
+    } else {
+      TabView* tabView = [_tabArray objectAtIndex:tabIndex];
+      CGRect scrollRect =
+          CGRectInset(tabView.frame, -_tabStripView.contentInset.right, 0);
+      if (tabView)
+        [_tabStripView scrollRectToVisible:scrollRect animated:YES];
+    }
+  }
+}
+
+- (void)updateScrollViewFrameForToggleButton {
+  CGRect tabFrame = _tabStripView.frame;
+  tabFrame.size.width = _view.bounds.size.width;
+  if (!IsCompactTablet()) {
+    if (_modeToggleButton)
+      tabFrame.size.width -= kModeToggleButtonWidth;
+    if (_tabSwitcherToggleButton)
+      tabFrame.size.width -= kTabSwitcherToggleButtonWidth;
+    _tabStripView.contentInset = UIEdgeInsetsZero;
+    [_toggleButtonBackgroundView setHidden:YES];
+  } else {
+    if (!_toggleButtonBackgroundView) {
+      _toggleButtonBackgroundView.reset([[UIImageView alloc] init]);
+      const CGFloat tabStripHeight = _view.frame.size.height;
+      const CGRect backgroundViewFrame = CGRectMake(
+          CGRectGetMaxX(_view.frame) - kModeToggleButtonBackgroundWidth, 0.0,
+          kModeToggleButtonBackgroundWidth, tabStripHeight);
+      [_toggleButtonBackgroundView setFrame:backgroundViewFrame];
+      [_toggleButtonBackgroundView
+          setAutoresizingMask:UIViewAutoresizingFlexibleLeftMargin];
+      UIImage* backgroundToggleImage =
+          [UIImage imageNamed:@"tabstrip_toggle_button_gradient"];
+      [_toggleButtonBackgroundView setImage:backgroundToggleImage];
+      [_view addSubview:_toggleButtonBackgroundView];
+    }
+    const BOOL hasModeToggleButton =
+        _modeToggleButton || _tabSwitcherToggleButton;
+    [_toggleButtonBackgroundView setHidden:!hasModeToggleButton];
+    if (!hasModeToggleButton)
+      _tabStripView.contentInset = UIEdgeInsetsZero;
+    if (_modeToggleButton) {
+      _tabStripView.contentInset =
+          UIEdgeInsetsMake(0, 0, 0, kModeToggleButtonWidth);
+      [_view bringSubviewToFront:_modeToggleButton];
+    }
+    if (_tabSwitcherToggleButton) {
+      _tabStripView.contentInset =
+          UIEdgeInsetsMake(0, 0, 0, kTabSwitcherToggleButtonWidth);
+      [_view bringSubviewToFront:_tabSwitcherToggleButton];
+    }
+  }
+  [_tabStripView setFrame:tabFrame];
+}
+
+#pragma mark - TabStripViewLayoutDelegate
+
+// Creates TabViews for each Tab in the TabModel and positions them in the
+// correct location onscreen.
+- (void)layoutTabStripSubviews {
+  const NSUInteger tabCount = [_tabArray count] - [_closingTabs count];
+  if (!tabCount)
+    return;
+  BOOL animate = _animateLayout;
+  _animateLayout = NO;
+  // Disable the animation if the tab count is changing from 0 to 1.
+  if (tabCount == 1 && [_closingTabs count] == 0)
+    animate = NO;
+
+  const CGFloat tabHeight = CGRectGetHeight([_tabStripView bounds]);
+
+  // In compact layout mode the space used to layout the tabs is not
+  // constrained and uses the whole scroll view content size width. In regular
+  // layout mode the available space is constrained to the visible space.
+  CGFloat availableSpace = IsCompactTablet() ? _tabStripView.contentSize.width
+                                             : [self tabStripVisibleSpace];
+
+  // The array and model indexes of the selected tab.
+  NSUInteger selectedModelIndex = [_tabModel indexOfTab:[_tabModel currentTab]];
+  NSUInteger selectedArrayIndex = [self indexForModelIndex:selectedModelIndex];
+
+  // This method lays out tabs in two coordinate systems.  The first, the
+  // "virtual" coordinate system, is a system rooted at x=0 that contains all
+  // the tabs laid out as if the tabstrip was infinitely long.  In this system,
+  // |virtualMinX| contains the starting X coordinate of the next tab to be
+  // placed and |virtualMaxX| contains the maximum X coordinate of the last tab
+  // to be placed.
+  //
+  // The scroll view's content area is sized to be large enough to hold all the
+  // tabs with proper overlap, but the viewport is set to only show a part of
+  // the content area.  The specific part that is shown is given by the scroll
+  // view's contentOffset.
+  //
+  // To layout tabs, first calculate where the tab should be in the "virtual"
+  // coordinate system.  This gives the frame of the tab assuming the tabstrip
+  // was large enough to hold all tabs without needing to overflow.  Then,
+  // adjust the tab's virtual frame to move it onscreen.  This gives the tab's
+  // real frame.
+  CGFloat virtualMinX = 0;
+  CGFloat virtualMaxX = 0;
+  CGFloat offset = IsCompactTablet() ? 0 : [_tabStripView contentOffset].x;
+
+  // Keeps track of which tabs need to be animated.  Using an autoreleased array
+  // instead of scoped_nsobject because scoped_nsobject doesn't seem to work
+  // well with blocks.
+  NSMutableArray* tabsNeedingAnimation =
+      [NSMutableArray arrayWithCapacity:tabCount];
+
+  CGRect dragFrame = [_draggedTab frame];
+
+  TabView* previousTabView = nil;
+  CGRect previousTabFrame = CGRectZero;
+  BOOL hasPlaceholderGap = NO;
+  for (NSUInteger arrayIndex = 0; arrayIndex < [_tabArray count];
+       ++arrayIndex) {
+    TabView* view = (TabView*)[_tabArray objectAtIndex:arrayIndex];
+
+    // Arrange the tabs in a V going backwards from the selected tab.  This
+    // differs from desktop in order to make the tab overflow behavior work (on
+    // desktop, the tabs are arranged going backwards from left to right, with
+    // the selected tab above all others).
+    //
+    // When reordering, use slightly different logic.  Instead of a V based on
+    // the model indexes of the tabs, the V fans out from the placeholder gap,
+    // which is visually where the dragged tab is.  In reordering mode, the tabs
+    // are not necessarily z-ordered according to their model indexes, because
+    // they are not necessarily drawn in the spot dictated by their current
+    // model index.
+    BOOL isSelectedTab = (arrayIndex == selectedArrayIndex);
+    BOOL zOrderedAbove =
+        _isReordering ? !hasPlaceholderGap : (arrayIndex <= selectedArrayIndex);
+
+    if (isSelectedTab) {
+      // Order matters.  The dimming view needs to end up behind the selected
+      // tab, so it's brought to the front first, followed by the tab.
+      [_tabStripView bringSubviewToFront:_dimmingView];
+      [_tabStripView bringSubviewToFront:view];
+    } else if (zOrderedAbove) {
+      // If the current tab comes after the selected tab in the model but still
+      // needs to be z-ordered above, place it relative to the dimming view,
+      // rather than blindly bringing it to the front.  This can only happen in
+      // reordering mode.
+      if (arrayIndex > selectedArrayIndex) {
+        DCHECK(_isReordering);
+        [_tabStripView insertSubview:view belowSubview:_dimmingView];
+      } else {
+        [_tabStripView bringSubviewToFront:view];
+      }
+    } else {
+      [_tabStripView sendSubviewToBack:view];
+    }
+
+    // Ignore closing tabs when repositioning.
+    NSUInteger currentModelIndex = [self modelIndexForIndex:arrayIndex];
+    if (currentModelIndex == NSNotFound)
+      continue;
+
+    // Ignore the tab that is currently being dragged.
+    if (_isReordering && view == _draggedTab)
+      continue;
+
+    // |realMinX| is the furthest left the tab can be, in real coordinates.
+    // This is computed by counting the number of possible collapsed tabs that
+    // can be to the left of this tab, then multiplying that count by the size
+    // of a collapsed tab.
+    //
+    // There can be up to |[self maxNumCollapsedTabs]| to the left of the
+    // selected
+    // tab, and the same number to the right of the selected tab.
+    NSUInteger numPossibleCollapsedTabsToLeft =
+        std::min(currentModelIndex, [self maxNumCollapsedTabs]);
+    if (currentModelIndex > selectedModelIndex) {
+      // If this tab is to the right of the selected tab, also include the
+      // number of collapsed tabs on the right of the selected tab.
+      numPossibleCollapsedTabsToLeft =
+          std::min(selectedModelIndex, [self maxNumCollapsedTabs]) +
+          std::min(currentModelIndex - selectedModelIndex,
+                   [self maxNumCollapsedTabs]);
+    }
+    CGFloat realMinX =
+        offset + (numPossibleCollapsedTabsToLeft * kCollapsedTabOverlap);
+
+    // |realMaxX| is the furthest right the tab can be, in real coordinates.
+    NSUInteger numPossibleCollapsedTabsToRight =
+        std::min(tabCount - currentModelIndex - 1, [self maxNumCollapsedTabs]);
+    if (currentModelIndex < selectedModelIndex) {
+      // If this tab is to the left of the selected tab, also include the
+      // number of collapsed tabs on the left of the selected tab.
+      numPossibleCollapsedTabsToRight =
+          std::min(tabCount - selectedModelIndex - 1,
+                   [self maxNumCollapsedTabs]) +
+          std::min(selectedModelIndex - currentModelIndex,
+                   [self maxNumCollapsedTabs]);
+    }
+    CGFloat realMaxX = offset + availableSpace -
+                       (numPossibleCollapsedTabsToRight * kCollapsedTabOverlap);
+
+    // If this tab is to the right of the currently dragged tab, add a
+    // placeholder gap.
+    if (_isReordering && !hasPlaceholderGap &&
+        CGRectGetMinX(dragFrame) < virtualMinX + (_currentTabWidth / 2.0)) {
+      virtualMinX += _currentTabWidth - [self tabOverlap];
+      hasPlaceholderGap = YES;
+
+      // Fix up the z-ordering of the current view.  It was placed assuming that
+      // the placeholder gap hasn't been hit yet.
+      [_tabStripView sendSubviewToBack:view];
+
+      // The model index of the placeholder gap is equal to the model index of
+      // the shifted tab, adjusted for the presence of the dragged tab.  This
+      // value will be used as the new model index for the dragged tab when it
+      // is dropped.
+      _placeholderGapModelIndex = currentModelIndex;
+      if ([self modelIndexForTabView:_draggedTab] < currentModelIndex)
+        _placeholderGapModelIndex--;
+    }
+
+    // |tabX| stores where we are placing the tab, in real coordinates.  Start
+    // by trying to place the tab at the computed |virtualMinX|, then constrain
+    // that by |realMinX| and |realMaxX|.
+    CGFloat tabX = MAX(virtualMinX, realMinX);
+    if (tabX + _currentTabWidth > realMaxX)
+      tabX = realMaxX - _currentTabWidth;
+
+    CGRect frame = CGRectMake(AlignValueToPixel(tabX), 0,
+                              AlignValueToPixel(_currentTabWidth), tabHeight);
+    virtualMinX += (_currentTabWidth - [self tabOverlap]);
+    virtualMaxX = CGRectGetMaxX(frame);
+
+// TODO(rohitrao): Temporarily disabled this logic as it does not play well with
+// tab scrolling.
+#if 0
+    // If this tab is completely hidden by the previous tab, remove it from the
+    // scroll view.  Otherwise, add it back in if needed.
+    if (selectedArrayIndex != arrayIndex &&
+        CGRectEqualToRect(frame, previousTabFrame)) {
+      [view removeFromSuperview];
+    } else if (![view superview]) {
+      // TODO(rohitrao): Find a way to move the z-ordering code from the top of
+      // the function to down here, so we can consolidate the logic.
+      [_tabStripView insertSubview:view atIndex:
+                       (zOrderedAbove ? [[_tabStripView subviews] count] : 0)];
+    }
+#endif
+
+    // Update the tab's collapsed state based on overlap with the previous tab.
+    if (zOrderedAbove) {
+      CGRect visibleRect = [self calculateVisibleFrameForFrame:previousTabFrame
+                                                whenUnderFrame:frame];
+      BOOL collapsed =
+          CGRectGetWidth(visibleRect) < kCollapsedTabWidthThreshold;
+      [previousTabView setCollapsed:collapsed];
+
+      // The selected tab can never be collapsed, since no tab will ever be
+      // z-ordered above it to obscure it.
+      if (isSelectedTab)
+        [view setCollapsed:NO];
+    } else {
+      CGRect visibleRect =
+          [self calculateVisibleFrameForFrame:frame
+                               whenUnderFrame:previousTabFrame];
+      BOOL collapsed =
+          CGRectGetWidth(visibleRect) < kCollapsedTabWidthThreshold;
+      [view setCollapsed:collapsed];
+    }
+
+    if (animate) {
+      if (!CGRectEqualToRect(frame, [view frame]))
+        [tabsNeedingAnimation addObject:view];
+    } else {
+      if (!CGRectEqualToRect(frame, [view frame]))
+        [view setFrame:frame];
+    }
+
+    // Throw the target frame into the dictionary so we can animate it later.
+    _targetFrames.AddFrame(view, frame);
+
+    // Ensure the tab is visible.
+    if ([view isHidden]) {
+      if (animate) {
+        // If it is a new tab, and animation is enabled, make it a submarine tab
+        // by immediately positioning it under the tabstrip.
+        CGRect submarineFrame = CGRectOffset(frame, 0, CGRectGetHeight(frame));
+        [view setFrame:submarineFrame];
+      }
+      [view setHidden:NO];
+    }
+
+    previousTabView = view;
+    previousTabFrame = frame;
+  }
+
+  // If in reordering mode and there was no placeholder gap, then the dragged
+  // tab must be all the way to the right of the other tabs.  Set the
+  // _placeholderGapModelIndex accordingly.
+  if (!hasPlaceholderGap && _isReordering)
+    _placeholderGapModelIndex = [_tabModel count] - 1;
+
+  // Do not move the new tab button if it is hidden.  This will lead to better
+  // animations when exiting drag and drop mode, as the new tab button will not
+  // have moved during the drag.
+  CGRect newTabFrame = [_buttonNewTab frame];
+  BOOL moveNewTab =
+      (newTabFrame.origin.x != virtualMaxX) && !_buttonNewTab.hidden;
+  newTabFrame.origin = CGPointMake(virtualMaxX - kNewTabOverlap, 0);
+  if (!animate && moveNewTab)
+    [_buttonNewTab setFrame:newTabFrame];
+
+  if (animate) {
+    float delay = 0.0;
+    if ([self.fullscreenDelegate currentHeaderOffset] != 0) {
+      // Move the toolbar to visible and wait for the end of that animation to
+      // animate the appearance of the new tab.
+      delay = ios_internal::kToolbarAnimationDuration;
+      // Signal the FullscreenController that the toolbar needs to stay on
+      // screen for a bit, so the animation is visible.
+      [[NSNotificationCenter defaultCenter]
+          postNotificationName:kWillStartTabStripTabAnimation
+                        object:nil];
+    }
+
+    [UIView animateWithDuration:kTabAnimationDuration
+                          delay:delay
+                        options:UIViewAnimationOptionAllowUserInteraction
+                     animations:^{
+                       for (TabView* view in tabsNeedingAnimation) {
+                         DCHECK(_targetFrames.HasFrame(view));
+                         [view setFrame:_targetFrames.GetFrame(view)];
+                       }
+                       if (moveNewTab)
+                         [_buttonNewTab setFrame:newTabFrame];
+                     }
+                     completion:nil];
+  }
+}
+
+- (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
+  [self updateScrollViewFrameForToggleButton];
+  [self updateContentSizeAndRepositionViews];
+  NSUInteger selectedModelIndex = [_tabModel indexOfTab:[_tabModel currentTab]];
+  if (selectedModelIndex != NSNotFound) {
+    [self updateContentOffsetForTabIndex:selectedModelIndex];
+  }
+}
+
+- (void)setNeedsLayoutWithAnimation {
+  _animateLayout = YES;
+  [_tabStripView setNeedsLayout];
+}
+
+@end
+
+#pragma mark - TabSwitcherAnimation
+
+@implementation TabStripController (TabSwitcherAnimation)
+
+- (TabSwitcherTabStripPlaceholderView*)placeholderView {
+  TabSwitcherTabStripPlaceholderView* placeholderView =
+      [[[TabSwitcherTabStripPlaceholderView alloc]
+          initWithFrame:self.view.bounds] autorelease];
+  CGFloat xOffset = [_tabStripView contentOffset].x;
+  UIView* previousView = nil;
+  const NSUInteger selectedModelIndex =
+      [_tabModel indexOfTab:[_tabModel currentTab]];
+  const NSUInteger selectedArrayIndex =
+      [self indexForModelIndex:selectedModelIndex];
+  [self updateContentSizeAndRepositionViews];
+  [self layoutTabStripSubviews];
+  for (NSUInteger tabArrayIndex = 0; tabArrayIndex < [_tabArray count];
+       ++tabArrayIndex) {
+    UIView* tabView = _tabArray[tabArrayIndex];
+    UIView* tabSnapshotView = snapshot_util::GenerateSnapshot(tabView);
+    tabSnapshotView.frame = CGRectOffset(tabView.frame, -xOffset, 0);
+    tabSnapshotView.transform = tabView.transform;
+    // Order views of the tabs in a pyramid fashion, culminating with
+    // the selected tab.
+    // For example, if _tabArray has views [0..6], and 3 is the selected index,
+    // they will be arranged in the order [0, 1, 2, 6, 5, 4, 3].
+    if (previousView && tabArrayIndex > selectedArrayIndex) {
+      [placeholderView insertSubview:tabSnapshotView belowSubview:previousView];
+    } else {
+      [placeholderView addSubview:tabSnapshotView];
+    }
+    previousView = tabSnapshotView;
+  }
+  UIView* buttonSnapshot = snapshot_util::GenerateSnapshot(_buttonNewTab);
+  buttonSnapshot.frame = CGRectOffset(_buttonNewTab.frame, -xOffset, 0);
+  [placeholderView addSubview:buttonSnapshot];
+  return placeholderView;
+}
+
+@end
+
+@implementation TabStripController (Testing)
+
+- (TabView*)existingTabViewForTab:(Tab*)tab {
+  NSUInteger tabIndex = [_tabModel indexOfTab:tab];
+  NSUInteger tabViewIndex = [self indexForModelIndex:tabIndex];
+  return [_tabArray objectAtIndex:tabViewIndex];
+}
+
+@end