P2.1a.

chrome/browser/cocoa/hover_close_button.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.
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/scoped_nsobject.h"
 
+@class TabController;
+
 // The standard close button for our Mac UI which is the "x"
 // that changes to the red circle with the "x" when you hover over it.
 // At this time it is used by the popup blocker, download bar, info bar
 // and tabs.
 @interface HoverCloseButton : NSButton {
   // Tracking area for close button mouseover images.
   scoped_nsobject<NSTrackingArea> closeTrackingArea_;
+
+  IBOutlet TabController* controller_;
 }
 
 // Enables or disables the |NSTrackingRect|s for the button.
 - (void)setTrackingEnabled:(BOOL)enabled;
 
 // Sets up the button's images, tracking areas, and accessibility info
 // when instantiated via initWithFrame or awakeFromNib.
 - (void)commonInit;
 
 // 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 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