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

chrome/browser/cocoa/tab_view.h

Index: chrome/browser/cocoa/tab_view.h
===================================================================
--- chrome/browser/cocoa/tab_view.h	(revision 16861)
+++ chrome/browser/cocoa/tab_view.h	(working copy)
@@ -7,6 +7,8 @@
 
 #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
@@ -20,6 +22,9 @@
   // 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?