fix for 27454 - Fade out close button state on mouse exit

chrome/browser/ui/cocoa/hover_button.h

 // Copyright (c) 2011 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 <Cocoa/Cocoa.h>
 
 #include "base/memory/scoped_nsobject.h"
+#include "chrome/browser/ui/cocoa/tracking_area.h"
+
 
 // A button that changes when you hover over it and click it.
 @interface HoverButton : NSButton {
  @protected
   // Enumeration of the hover states that the close button can be in at any one
   // time. The button cannot be in more than one hover state at a time.
   enum HoverState {
     kHoverStateNone = 0,
     kHoverStateMouseOver = 1,
     kHoverStateMouseDown = 2
   };
 
   HoverState hoverState_;
 
  @private
   // Tracking area for button mouseover states.
-  scoped_nsobject<NSTrackingArea> trackingArea_;
+  ScopedCrTrackingArea trackingArea_;
 }
 
-// Enables or disables the |NSTrackingRect|s for the button.
+@property(nonatomic) HoverState hoverState;
+
+// Enables or disables the tracking for the button.
 - (void)setTrackingEnabled:(BOOL)enabled;
 
 // Checks to see whether the mouse is in the button's bounds and update
 // the image in case it gets out of sync.  This occurs to the close button
 // when you close a tab so the tab to the left of it takes its place, and
 // drag the button without moving the mouse before you press the button down.
 - (void)checkImageState;
 @end