Mac: Make it easier for views to correctly draw with a theme.

chrome/browser/ui/cocoa/tabs/tab_strip_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_STRIP_VIEW_H_
 #define CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_VIEW_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/mac/scoped_nsobject.h"
-#import "chrome/browser/ui/cocoa/background_gradient_view.h"
+#import "chrome/browser/ui/cocoa/themed_window.h"
 #import "chrome/browser/ui/cocoa/url_drop_target.h"
 
 @class NewTabButton;
 @class TabStripController;
 
 // A view class that handles rendering the tab strip and drops of URLS with
 // a positioning locator for drop feedback.
 
-@interface TabStripView : BackgroundGradientView<URLDropTarget> {
+@interface TabStripView : NSView<ThemedWindowDrawing, URLDropTarget> {

[Andre, 2015/02/03 19:13:19]

See https://codereview.chromium.org/867273003/ for why the superclass is
changed.

  @private
   TabStripController* controller_;  // Weak; owns us.
 
   NSTimeInterval lastMouseUp_;
 
   // Handles being a drag-and-drop target.
   base::scoped_nsobject<URLDropTargetHandler> dropHandler_;
 
   base::scoped_nsobject<NewTabButton> newTabButton_;
 
@@ skipping 22 matching lines @@
 @interface TabStripView (Protected)
 - (void)drawBottomBorder:(NSRect)bounds;
 - (BOOL)doubleClickMinimizesWindow;
 @end
 
 @interface TabStripView (TestingAPI)
 - (void)setNewTabButton:(NewTabButton*)button;
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TABS_TAB_STRIP_VIEW_H_