mac: UI tweaks to tab overview mode

chrome/browser/ui/cocoa/tabpose_window.h

 // Copyright (c) 2010 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_TABPOSE_WINDOW_H_
 #define CHROME_BROWSER_UI_COCOA_TABPOSE_WINDOW_H_
 #pragma once
 
 #import <Cocoa/Cocoa.h>
 
@@ skipping 30 matching lines @@
 @interface TabposeWindow : NSWindow {
  @private
   tabpose::WindowState state_;
 
   // The root layer added to the content view. Covers the whole window.
   CALayer* rootLayer_;  // weak
 
   // The layer showing the background layer. Covers the whole visible area.
   CALayer* bgLayer_;  // weak
 
+  // Top gradient.
+  CALayer* topGradient_;  // weak
+
   // The layer drawn behind the currently selected tile.
   CALayer* selectionHighlight_;  // weak
 
   // Colors used by the layers.
   base::mac::ScopedCFTypeRef<CGColorRef> gray_;
   base::mac::ScopedCFTypeRef<CGColorRef> darkBlue_;
 
   TabStripModel* tabStripModel_;  // weak
 
   // Stores all preview layers. The order in here matches the order in
@@ skipping 31 matching lines @@
        tabStripModel:(TabStripModel*)tabStripModel;
 @end
 
 @interface TabposeWindow (TestingAPI)
 - (void)selectTileAtIndexWithoutAnimation:(int)newIndex;
 - (NSUInteger)thumbnailLayerCount;
 - (int)selectedIndex;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABPOSE_WINDOW_H_