Adds mouseover images to the close tab button on Mac....

chrome/browser/cocoa/tab_view.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_BROWSER_COCOA_TAB_VIEW_H_
 #define CHROME_BROWSER_COCOA_TAB_VIEW_H_
 
 #import <Cocoa/Cocoa.h>
 
+#include "base/scoped_nsobject.h"
+
 @class TabController, TabWindowController;
 
 // A view that handles the event tracking (clicking and dragging) for a tab
 // on the tab strip. Relies on an associated TabController to provide a
 // target/action for selecting the tab.
 
 @interface TabView : NSView {
  @private
   IBOutlet TabController* controller_;
   // TODO(rohitrao): Add this button to a CoreAnimation layer so we can fade it
   // in and out on mouseovers.
   IBOutlet NSButton* closeButton_;
 
+  // Tracking area for close button mouseover images.
+  scoped_nsobject<NSTrackingArea> trackingArea_;
+
   // All following variables are valid for the duration of a drag.
   // These are released on mouseUp:
   BOOL isTheOnlyTab_;  // Is this the only tab in the window?
   BOOL tabWasDragged_;  // Has the tab been dragged?
   BOOL draggingWithinTabStrip_;  // Did drag stay in the current tab strip?
   BOOL chromeIsVisible_;
 
   NSTimeInterval tearTime_;  // Time since tear happened
   NSPoint tearOrigin_;  // Origin of the tear rect
   NSPoint dragOrigin_;  // Origin point of the drag
   // TODO(alcor): these references may need to be strong to avoid crashes
   // due to JS closing windows
   TabWindowController* sourceController_;  // weak. controller starting the drag
   NSWindow* sourceWindow_;  // weak. The window starting the drag
   NSRect sourceWindowFrame_;
   NSRect sourceTabFrame_;
 
   TabWindowController* draggedController_;  // weak. Controller being dragged.
   NSWindow* dragWindow_;  // weak. The window being dragged
   NSWindow* dragOverlay_;  // weak. The overlay being dragged
 
   TabWindowController* targetController_;  // weak. Controller being targeted
 }
 @end
 
 #endif  // CHROME_BROWSER_COCOA_TAB_VIEW_H_