Upstream Chrome on iOS source code [8/11].

ios/chrome/browser/ui/settings/settings_navigation_controller.mm

+// Copyright 2013 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/settings/settings_navigation_controller.h"
+
+#include "base/ios/ios_util.h"
+#import "base/ios/weak_nsobject.h"
+#include "base/mac/foundation_util.h"
+#import "base/mac/scoped_nsobject.h"
+#include "components/strings/grit/components_strings.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state.h"
+#include "ios/chrome/browser/sync/sync_setup_service.h"
+#include "ios/chrome/browser/sync/sync_setup_service_factory.h"
+#import "ios/chrome/browser/ui/commands/UIKit+ChromeExecuteCommand.h"
+#import "ios/chrome/browser/ui/commands/clear_browsing_data_command.h"
+#include "ios/chrome/browser/ui/commands/ios_command_ids.h"
+#import "ios/chrome/browser/ui/commands/show_signin_command.h"
+#import "ios/chrome/browser/ui/icons/chrome_icon.h"
+#import "ios/chrome/browser/ui/keyboard/UIKeyCommand+Chrome.h"
+#import "ios/chrome/browser/ui/material_components/app_bar_presenting.h"
+#import "ios/chrome/browser/ui/material_components/utils.h"
+#import "ios/chrome/browser/ui/settings/accounts_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/clear_browsing_data_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/contextual_search_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/import_data_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/native_apps_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/save_passwords_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/settings_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/settings_utils.h"
+#import "ios/chrome/browser/ui/settings/sync_encryption_passphrase_collection_view_controller.h"
+#import "ios/chrome/browser/ui/settings/sync_settings_collection_view_controller.h"
+#include "ios/chrome/browser/ui/ui_util.h"
+#import "ios/chrome/browser/ui/uikit_ui_util.h"
+#include "ios/chrome/grit/ios_strings.h"
+#include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
+#import "ios/public/provider/chrome/browser/user_feedback/user_feedback_provider.h"
+#import "ios/third_party/material_components_ios/src/components/AppBar/src/MaterialAppBar.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/base/l10n/l10n_util_mac.h"
+
+// TODO(crbug.com/620361): Remove the entire class when iOS 9 is dropped.
+@interface SettingsAppBarContainerViewController
+    : MDCAppBarContainerViewController
+@end
+
+@implementation SettingsAppBarContainerViewController
+
+#pragma mark - Status bar
+
+- (UIViewController*)childViewControllerForStatusBarHidden {
+  if (!base::ios::IsRunningOnIOS10OrLater()) {
+    // TODO(crbug.com/620361): Remove the entire method override when iOS 9 is
+    // dropped.
+    return self.contentViewController;
+  } else {
+    return [super childViewControllerForStatusBarHidden];
+  }
+}
+
+- (UIViewController*)childViewControllerForStatusBarStyle {
+  if (!base::ios::IsRunningOnIOS10OrLater()) {
+    // TODO(crbug.com/620361): Remove the entire method override when iOS 9 is
+    // dropped.
+    return self.contentViewController;
+  } else {
+    return [super childViewControllerForStatusBarStyle];
+  }
+}
+
+@end
+
+@interface SettingsNavigationController ()<UIGestureRecognizerDelegate>
+
+// Sets up the UI.  Used by both initializers.
+- (void)configureUI;
+
+// Closes the settings by calling |closeSettings| on |delegate|.
+- (void)closeSettings;
+
+// Creates an autoreleased "X" button that closes the settings when tapped.
+- (UIBarButtonItem*)closeButton;
+
+// Creates an autoreleased "CANCEL" button that closes the settings when tapped.
+- (UIBarButtonItem*)cancelButton;
+
+// Intercepts the chrome command |sender|. If |sender| is an
+// |IDC_CLOSE_SETTINGS_AND_OPEN_URL| and |delegate_| is not nil, then it
+// calls [delegate closeSettingsAndOpenUrl:sender], otherwise it forwards the
+// command up the responder chain.
+- (void)chromeExecuteCommand:(id)sender;
+
+@end
+
+@implementation SettingsNavigationController {
+  ios::ChromeBrowserState* mainBrowserState_;  // weak
+  base::WeakNSProtocol<id<SettingsNavigationControllerDelegate>> delegate_;
+  // Keeps a mapping between the view controllers that are wrapped to display an
+  // app bar and the containers that wrap them.
+  base::scoped_nsobject<NSMutableDictionary> appBarContainedViewControllers_;
+}
+
+@synthesize shouldCommitSyncChangesOnDismissal =
+    shouldCommitSyncChangesOnDismissal_;
+
+#pragma mark - SettingsNavigationController methods.
+
+// clang-format off
++ (SettingsNavigationController*)newSettingsMainControllerWithMainBrowserState:
+    (ios::ChromeBrowserState*)browserState
+                                                           currentBrowserState:
+    (ios::ChromeBrowserState*)currentBrowserState
+                                                                      delegate:
+    (id<SettingsNavigationControllerDelegate>)delegate {
+  // clang-format on
+  base::scoped_nsobject<UIViewController> controller(
+      [[SettingsCollectionViewController alloc]
+          initWithBrowserState:browserState
+           currentBrowserState:currentBrowserState]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc doneButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newAccountsController:(ios::ChromeBrowserState*)browserState
+             delegate:(id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller([
+      [AccountsCollectionViewController alloc] initWithBrowserState:browserState
+                                          closeSettingsOnAddAccount:YES]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].leftBarButtonItem = [nc closeButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+     newSyncController:(ios::ChromeBrowserState*)browserState
+allowSwitchSyncAccount:(BOOL)allowSwitchSyncAccount
+              delegate:(id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[SyncSettingsCollectionViewController alloc]
+            initWithBrowserState:browserState
+          allowSwitchSyncAccount:allowSwitchSyncAccount]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc doneButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newUserFeedbackController:(ios::ChromeBrowserState*)browserState
+                 delegate:(id<SettingsNavigationControllerDelegate>)delegate
+       feedbackDataSource:(id<UserFeedbackDataSource>)dataSource {
+  DCHECK(ios::GetChromeBrowserProvider()
+             ->GetUserFeedbackProvider()
+             ->IsUserFeedbackEnabled());
+  base::scoped_nsobject<UIViewController> controller(
+      ios::GetChromeBrowserProvider()
+          ->GetUserFeedbackProvider()
+          ->CreateViewController(dataSource));
+  DCHECK(controller);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc cancelButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newClearBrowsingDataController:(ios::ChromeBrowserState*)browserState
+                      delegate:
+                          (id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[ClearBrowsingDataCollectionViewController alloc]
+          initWithBrowserState:browserState]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc doneButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newContextualSearchController:(ios::ChromeBrowserState*)browserState
+                     delegate:
+                         (id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[ContextualSearchCollectionViewController alloc]
+          initWithBrowserState:browserState]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc doneButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newSyncEncryptionPassphraseController:(ios::ChromeBrowserState*)browserState
+                             delegate:(id<SettingsNavigationControllerDelegate>)
+                                          delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[SyncEncryptionPassphraseCollectionViewController alloc]
+          initWithBrowserState:browserState]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].leftBarButtonItem = [nc closeButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newNativeAppsController:(ios::ChromeBrowserState*)browserState
+               delegate:(id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[NativeAppsCollectionViewController alloc]
+          initWithURLRequestContextGetter:browserState->GetRequestContext()]);
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newSavePasswordsController:(ios::ChromeBrowserState*)browserState
+                  delegate:(id<SettingsNavigationControllerDelegate>)delegate {
+  base::scoped_nsobject<UIViewController> controller(
+      [[SavePasswordsCollectionViewController alloc]
+          initWithBrowserState:browserState]);
+
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+  [controller navigationItem].rightBarButtonItem = [nc doneButton];
+
+  // Make sure the close button is always present, as the Save Passwords screen
+  // isn't just shown from Settings.
+  [controller navigationItem].leftBarButtonItem = [nc closeButton];
+  return nc;
+}
+
++ (SettingsNavigationController*)
+newImportDataController:(ios::ChromeBrowserState*)browserState
+               delegate:(id<SettingsNavigationControllerDelegate>)delegate
+     importDataDelegate:(id<ImportDataControllerDelegate>)importDataDelegate
+              fromEmail:(NSString*)fromEmail
+                toEmail:(NSString*)toEmail
+             isSignedIn:(BOOL)isSignedIn {
+  base::scoped_nsobject<UIViewController> controller(
+      [[ImportDataCollectionViewController alloc]
+          initWithDelegate:importDataDelegate
+                 fromEmail:fromEmail
+                   toEmail:toEmail
+                isSignedIn:isSignedIn]);
+
+  SettingsNavigationController* nc = [[SettingsNavigationController alloc]
+      initWithRootViewController:controller
+                    browserState:browserState
+                        delegate:delegate];
+
+  // Make sure the close button is always present, as the Save Passwords screen
+  // isn't just shown from Settings.
+  [controller navigationItem].leftBarButtonItem = [nc closeButton];
+  return nc;
+}
+
+#pragma mark - Lifecycle
+
+- (instancetype)
+initWithRootViewController:(UIViewController*)rootViewController
+              browserState:(ios::ChromeBrowserState*)browserState
+                  delegate:(id<SettingsNavigationControllerDelegate>)delegate {
+  DCHECK(browserState);
+  DCHECK(!browserState->IsOffTheRecord());
+  self = [super initWithRootViewController:rootViewController];
+  if (self) {
+    mainBrowserState_ = browserState;
+    delegate_.reset(delegate);
+    shouldCommitSyncChangesOnDismissal_ = YES;
+    [self configureUI];
+  }
+  return self;
+}
+
+- (void)settingsWillBeDismissed {
+  // Notify all controllers that settings are about to be dismissed.
+  for (UIViewController* controller in [self viewControllers]) {
+    if ([controller respondsToSelector:@selector(settingsWillBeDismissed)]) {
+      [controller performSelector:@selector(settingsWillBeDismissed)];
+    }
+  }
+
+  // Sync changes cannot be cancelled and they must always be commited when
+  // existing settings.
+  if (shouldCommitSyncChangesOnDismissal_) {
+    SyncSetupServiceFactory::GetForBrowserState([self mainBrowserState])
+        ->CommitChanges();
+  }
+
+  // Reset the delegate to prevent any queued transitions from attempting to
+  // close the settings.
+  delegate_.reset();
+}
+
+- (void)closeSettings {
+  [delegate_ closeSettings];
+}
+
+- (void)popViewControllerOrCloseSettingsAnimated:(BOOL)animated {
+  if (self.viewControllers.count > 1) {
+    // Pop the top view controller to reveal the view controller underneath.
+    [self popViewControllerAnimated:animated];
+  } else {
+    // If there is only one view controller in the navigation stack,
+    // simply close settings.
+    [self closeSettings];
+  }
+}
+
+- (void)configureUI {
+  [self setModalPresentationStyle:UIModalPresentationFormSheet];
+  [self setModalTransitionStyle:UIModalTransitionStyleCoverVertical];
+  // Since the navigation bar is hidden, the gesture to swipe to go back can
+  // become inactive. Setting the delegate to self is an MDC workaround to have
+  // it consistently work with AppBar.
+  // https://github.com/material-components/material-components-ios/issues/720
+  [self setNavigationBarHidden:YES];
+  [self.interactivePopGestureRecognizer setDelegate:self];
+}
+
+- (BOOL)hasRightDoneButton {
+  UIBarButtonItem* rightButton =
+      self.topViewController.navigationItem.rightBarButtonItem;
+  if (!rightButton)
+    return NO;
+  base::scoped_nsobject<UIBarButtonItem> doneButton([self doneButton]);
+  return [rightButton style] == [doneButton style] &&
+         [[rightButton title] compare:[doneButton title]] == NSOrderedSame;
+}
+
+- (UIBarButtonItem*)doneButton {
+  // Create a custom Done bar button item, as Material Navigation Bar does not
+  // handle a system UIBarButtonSystemItemDone item.
+  return [[[UIBarButtonItem alloc]
+      initWithTitle:l10n_util::GetNSString(IDS_IOS_NAVIGATION_BAR_DONE_BUTTON)
+              style:UIBarButtonItemStyleDone
+             target:self
+             action:@selector(closeSettings)] autorelease];
+}
+
+- (UIBarButtonItem*)closeButton {
+  UIBarButtonItem* closeButton =
+      [ChromeIcon templateBarButtonItemWithImage:[ChromeIcon closeIcon]
+                                          target:self
+                                          action:@selector(closeSettings)];
+  closeButton.accessibilityLabel = l10n_util::GetNSString(IDS_ACCNAME_CLOSE);
+  return closeButton;
+}
+
+- (UIBarButtonItem*)cancelButton {
+  // Create a custom Cancel bar button item, as Material Navigation Bar does not
+  // handle a system UIBarButtonSystemItemCancel item.
+  return [[[UIBarButtonItem alloc]
+      initWithTitle:l10n_util::GetNSString(IDS_IOS_NAVIGATION_BAR_CANCEL_BUTTON)
+              style:UIBarButtonItemStyleDone
+             target:self
+             action:@selector(closeSettings)] autorelease];
+}
+
+- (UIInterfaceOrientationMask)supportedInterfaceOrientations {
+  return [self.topViewController supportedInterfaceOrientations];
+}
+
+- (BOOL)shouldAutorotate {
+  return [self.topViewController shouldAutorotate];
+}
+
+#pragma mark - UIGestureRecognizerDelegate
+
+- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer*)gestureRecognizer {
+  DCHECK_EQ(gestureRecognizer, self.interactivePopGestureRecognizer);
+  return self.viewControllers.count > 1;
+}
+
+#pragma mark - Accessibility
+
+- (BOOL)accessibilityPerformEscape {
+  UIViewController* poppedController = [self popViewControllerAnimated:YES];
+  if (!poppedController)
+    [self closeSettings];
+  return YES;
+}
+
+#pragma mark - UINavigationController
+
+- (void)pushViewController:(UIViewController*)viewController
+                  animated:(BOOL)animated {
+  // Wrap the view controller in an MDCAppBarContainerViewController if needed.
+  [super pushViewController:[self wrappedControllerIfNeeded:viewController]
+                   animated:animated];
+}
+
+- (UIViewController*)popViewControllerAnimated:(BOOL)animated {
+  UIViewController* viewController = [super popViewControllerAnimated:animated];
+  // Unwrap the view controller from its MDCAppBarContainerViewController if
+  // needed.
+  return [self unwrappedControllerIfNeeded:viewController];
+}
+
+- (NSArray*)popToViewController:(UIViewController*)viewController
+                       animated:(BOOL)animated {
+  // First, check if the view controller was wrapped in an app bar container.
+  MDCAppBarContainerViewController* appBarContainer =
+      [self appBarContainerForController:viewController];
+  // Pop the view controllers.
+  NSArray* poppedViewControllers =
+      [super popToViewController:appBarContainer ?: viewController
+                        animated:animated];
+  // Unwrap the popped view controllers from their
+  // MDCAppBarContainerViewController if needed.
+  NSMutableArray* viewControllers = [NSMutableArray array];
+  [poppedViewControllers
+      enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL* stop) {
+        [viewControllers
+            addObject:[self unwrappedControllerIfNeeded:viewController]];
+      }];
+  return viewControllers;
+}
+
+// Ensures that the keyboard is always dismissed during a navigation transition.
+- (BOOL)disablesAutomaticKeyboardDismissal {
+  return NO;
+}
+
+#pragma mark - UIResponder (ChromeExecuteCommand)
+
+- (void)chromeExecuteCommand:(id)sender {
+  switch ([sender tag]) {
+    case IDC_CLOSE_SETTINGS: {
+      [delegate_ closeSettings];
+      return;
+    }
+    case IDC_OPEN_URL:
+      NOTREACHED() << "You should probably use the command "
+                   << "IDC_CLOSE_SETTINGS_AND_OPEN_URL instead of IDC_OPEN_URL";
+    case IDC_CLOSE_SETTINGS_AND_OPEN_URL: {
+      [delegate_ closeSettingsAndOpenUrl:sender];
+      return;
+    }
+    case IDC_CLOSE_SETTINGS_AND_OPEN_NEW_INCOGNITO_TAB: {
+      [delegate_ closeSettingsAndOpenNewIncognitoTab];
+      return;
+    }
+    case IDC_SHOW_SIGNIN_IOS:
+      // Sign-in actions can only happen on the main browser state (not on
+      // incognito browser state), which is unique. The command can just be
+      // forwarded up the responder chain.
+      break;
+    case IDC_CLEAR_BROWSING_DATA_IOS: {
+      // Check that the data for the right browser state is being cleared before
+      // forwarding it up the responder chain.
+      ios::ChromeBrowserState* commandBrowserState =
+          [base::mac::ObjCCast<ClearBrowsingDataCommand>(sender) browserState];
+
+      // Clearing browsing data for the wrong profile is a destructive action.
+      // Executing it on the wrong profile is a privacy issue. Kill the
+      // app if this ever happens.
+      CHECK_EQ(commandBrowserState, [self mainBrowserState]);
+      break;
+    }
+    case IDC_RESET_ALL_WEBVIEWS:
+      // The command to reset all webview is not related to the browser state so
+      // it can just be forwarded it up the responder chain.
+      break;
+    case IDC_SHOW_ACCOUNTS_SETTINGS: {
+      base::scoped_nsobject<UIViewController> controller(
+          [[AccountsCollectionViewController alloc]
+                   initWithBrowserState:mainBrowserState_
+              closeSettingsOnAddAccount:NO]);
+      [self pushViewController:controller animated:YES];
+      return;
+    }
+    case IDC_SHOW_SYNC_SETTINGS: {
+      base::scoped_nsobject<UIViewController> controller(
+          [[SyncSettingsCollectionViewController alloc]
+                initWithBrowserState:mainBrowserState_
+              allowSwitchSyncAccount:YES]);
+      [self pushViewController:controller animated:YES];
+      return;
+    }
+    case IDC_SHOW_SYNC_PASSPHRASE_SETTINGS: {
+      base::scoped_nsobject<UIViewController> controller(
+          [[SyncEncryptionPassphraseCollectionViewController alloc]
+              initWithBrowserState:mainBrowserState_]);
+      [self pushViewController:controller animated:YES];
+      return;
+    }
+    default:
+      NOTREACHED()
+          << "Unexpected command " << [sender tag]
+          << " Settings commands must execute on the main browser state.";
+  }
+  [[self nextResponder] chromeExecuteCommand:sender];
+}
+
+#pragma mark - UIResponder
+
+- (NSArray*)keyCommands {
+  base::WeakNSObject<SettingsNavigationController> weakSelf(self);
+  return @[
+    [UIKeyCommand cr_keyCommandWithInput:UIKeyInputEscape
+                           modifierFlags:Cr_UIKeyModifierNone
+                                   title:nil
+                                  action:^{
+                                    [weakSelf closeSettings];
+                                  }],
+  ];
+}
+
+#pragma mark - Profile
+
+- (ios::ChromeBrowserState*)mainBrowserState {
+  return mainBrowserState_;
+}
+
+#pragma mark - Status bar
+
+- (BOOL)modalPresentationCapturesStatusBarAppearance {
+  if (!base::ios::IsRunningOnIOS10OrLater()) {
+    // TODO(crbug.com/620361): Remove the entire method override when iOS 9 is
+    // dropped.
+    return YES;
+  } else {
+    return [super modalPresentationCapturesStatusBarAppearance];
+  }
+}
+
+- (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
+  [super traitCollectionDidChange:previousTraitCollection];
+  if (!base::ios::IsRunningOnIOS10OrLater()) {
+    // TODO(crbug.com/620361): Remove the entire method override when iOS 9 is
+    // dropped.
+    [self setNeedsStatusBarAppearanceUpdate];
+  }
+}
+
+#pragma mark - AppBar Containment
+
+// If viewController doesn't implement the AppBarPresenting protocol, it is
+// wrapped in an MDCAppBarContainerViewController, which is returned. Otherwise,
+// viewController is returned.
+- (UIViewController*)wrappedControllerIfNeeded:(UIViewController*)controller {
+  // If the controller can't be presented with an app bar, it needs to be
+  // wrapped in an MDCAppBarContainerViewController.
+  if (![controller conformsToProtocol:@protocol(AppBarPresenting)]) {
+    MDCAppBarContainerViewController* appBarContainer =
+        [[[SettingsAppBarContainerViewController alloc]
+            initWithContentViewController:controller] autorelease];
+
+    // Configure the style.
+    ConfigureAppBarWithCardStyle(appBarContainer.appBar);
+
+    // Adjust the frame of the contained view controller's view to be below the
+    // app bar.
+    CGRect contentFrame = controller.view.frame;
+    CGSize headerSize = [appBarContainer.appBar.headerViewController.headerView
+        sizeThatFits:contentFrame.size];
+    contentFrame = UIEdgeInsetsInsetRect(
+        contentFrame, UIEdgeInsetsMake(headerSize.height, 0, 0, 0));
+    controller.view.frame = contentFrame;
+
+    // Register the app bar container and return it.
+    [self registerAppBarContainer:appBarContainer];
+    return appBarContainer;
+  } else {
+    return controller;
+  }
+}
+
+// If controller is an MDCAppBarContainerViewController, it returns its content
+// view controller. Otherwise, it returns viewController.
+- (UIViewController*)unwrappedControllerIfNeeded:(UIViewController*)controller {
+  MDCAppBarContainerViewController* potentialAppBarController =
+      base::mac::ObjCCast<MDCAppBarContainerViewController>(controller);
+  if (potentialAppBarController) {
+    // Unregister the app bar container and return it.
+    [self unregisterAppBarContainer:potentialAppBarController];
+    return [potentialAppBarController contentViewController];
+  } else {
+    return controller;
+  }
+}
+
+// Adds an app bar container in a dictionary mapping its content view
+// controller's pointer to itself.
+- (void)registerAppBarContainer:(MDCAppBarContainerViewController*)container {
+  if (!appBarContainedViewControllers_) {
+    appBarContainedViewControllers_.reset([[NSMutableDictionary alloc] init]);
+  }
+  NSValue* key = [self keyForController:[container contentViewController]];
+  [appBarContainedViewControllers_ setObject:container forKey:key];
+}
+
+// Removes the app bar container entry from the aforementioned dictionary.
+- (void)unregisterAppBarContainer:(MDCAppBarContainerViewController*)container {
+  NSValue* key = [self keyForController:[container contentViewController]];
+  [appBarContainedViewControllers_ removeObjectForKey:key];
+}
+
+// Returns the app bar container containing |controller| if it is contained.
+// Otherwise, returns nil.
+- (MDCAppBarContainerViewController*)appBarContainerForController:
+    (UIViewController*)controller {
+  NSValue* key = [self keyForController:controller];
+  return [appBarContainedViewControllers_ objectForKey:key];
+}
+
+// Returns the dictionary key to use when dealing with |controller|.
+- (NSValue*)keyForController:(UIViewController*)controller {
+  return [NSValue valueWithPointer:controller];
+}
+
+@end