Allow pages on the OSX app launcher to be turned while dragging.

ui/app_list/cocoa/app_list_pager_view.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 "ui/app_list/cocoa/app_list_pager_view.h"
 
 #include "base/mac/mac_util.h"
 #include "skia/ext/skia_utils_mac.h"
 #include "ui/app_list/app_list_constants.h"
 #include "ui/gfx/scoped_ns_graphics_context_save_gstate_mac.h"
 
 namespace {
 
 const CGFloat kButtonHeight = 6;
 const CGFloat kButtonCornerRadius = 2;
 const CGFloat kButtonStripPadding = 20;
 
 }  // namespace
 
 @interface AppListPagerView ()
 
 @property(assign, nonatomic) NSInteger hoveredSegment;
 
-- (NSInteger)segmentUnderEvent:(NSEvent*)theEvent;
+- (NSInteger)segmentUnderLocation:(NSPoint)locationInWindow;
 
 @end
 
 @interface AppListPagerCell : NSSegmentedCell;
 @end
 
 @implementation AppListPagerView
 
 @synthesize hoveredSegment = hoveredSegment_;
 
@@ skipping 10 matching lines @@
                                              NSTrackingMouseMoved |
                                              NSTrackingActiveInKeyWindow
                                        owner:self
                                     userInfo:nil]);
     [self addTrackingArea:trackingArea_.get()];
     hoveredSegment_ = -1;
   }
   return self;
 }
 
+- (NSInteger)findAndHighlightSegmentAtLocation:(NSPoint)locationInWindow {
+  NSInteger segment = [self segmentUnderLocation:locationInWindow];
+  [self setHoveredSegment:segment];
+  return segment;
+}
+
 - (void)setHoveredSegment:(NSInteger)segment {
   if (segment == hoveredSegment_)
     return;
 
   hoveredSegment_ = segment;
   [self setNeedsDisplay:YES];
   return;
 }
 
-- (NSInteger)segmentUnderEvent:(NSEvent*)theEvent {
+- (NSInteger)segmentUnderLocation:(NSPoint)locationInWindow {
   if ([self segmentCount] == 0)
     return -1;
 
-  NSPoint pointInView = [self convertPoint:[theEvent locationInWindow]
+  NSPoint pointInView = [self convertPoint:locationInWindow
                                   fromView:nil];
   if (![self mouse:pointInView inRect:[self bounds]])
     return -1;
 
   CGFloat segmentWidth = [self bounds].size.width / [self segmentCount];
   return pointInView.x / segmentWidth;
 }
 
 - (BOOL)isHoveredForSegment:(NSInteger)segment {
   return segment == hoveredSegment_;
 }
 
 - (void)mouseExited:(NSEvent*)theEvent {
   [self setHoveredSegment:-1];
 }
 
 - (void)mouseMoved:(NSEvent*)theEvent {
-  [self setHoveredSegment:[self segmentUnderEvent:theEvent]];
+  [self findAndHighlightSegmentAtLocation:[theEvent locationInWindow]];
 }
 
 - (void)mouseDown:(NSEvent*)theEvent {
   // Temporarily clear the highlight to give feedback.
   [self setHoveredSegment:-1];
 }
 
 // The stock NSSegmentedControl ignores any clicks outside the non-default
 // control height, so process all clicks here.
 - (void)mouseUp:(NSEvent*)theEvent {
-  [self setHoveredSegment:[self segmentUnderEvent:theEvent]];
+  [self findAndHighlightSegmentAtLocation:[theEvent locationInWindow]];
   if (hoveredSegment_ < 0)
     return;
 
   [self setSelectedSegment:hoveredSegment_];
   [[self target] performSelector:[self action]
                       withObject:self];
 }
 
 @end
 
@@ skipping 44 matching lines @@
     return;
 
   [gfx::SkColorToCalibratedNSColor(app_list::kPagerSelectedColor) set];
   if (selectedRatio < 0)
     frame.origin.x += frame.size.width + frame.size.width * selectedRatio;
   frame.size.width *= fabs(selectedRatio);
   NSRectFill(frame);
 }
 
 @end