Delete some unused code found by the clang static analyzer.

chrome/browser/ui/cocoa/tabs/tab_view.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.
 
 #ifndef CHROME_BROWSER_UI_COCOA_TABS_TAB_VIEW_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_VIEW_H_
 #pragma once
 
 #import <Cocoa/Cocoa.h>
 #include <ApplicationServices/ApplicationServices.h>
@@ skipping 30 matching lines @@
 
 @interface TabView : BackgroundGradientView {
  @private
   IBOutlet TabController* controller_;
   // TODO(rohitrao): Add this button to a CoreAnimation layer so we can fade it
   // in and out on mouseovers.
   IBOutlet HoverCloseButton* closeButton_;
 
   BOOL closing_;
 
-  // Tracking area for close button mouseover images.
-  scoped_nsobject<NSTrackingArea> closeTrackingArea_;
-
   BOOL isMouseInside_;  // Is the mouse hovering over?
   tabs::AlertState alertState_;
 
   CGFloat hoverAlpha_;  // How strong the hover glow is.
   NSTimeInterval hoverHoldEndTime_;  // When the hover glow will begin dimming.
 
   CGFloat alertAlpha_;  // How strong the alert glow is.
   NSTimeInterval alertHoldEndTime_;  // When the hover glow will begin dimming.
 
   NSTimeInterval lastGlowUpdate_;  // Time either glow was last updated.
@@ skipping 31 matching lines @@
 
 // The TabController |controller_| is not the only owner of this view. If the
 // controller is released before this view, then we could be hanging onto a
 // garbage pointer. To prevent this, the TabController uses this interface to
 // clear the |controller_| pointer when it is dying.
 @interface TabView (TabControllerInterface)
 - (void)setController:(TabController*)controller;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_VIEW_H_