chrome: Cleanup class/struct forward declarations

chrome/browser/ui/cocoa/extensions/browser_action_button.h

 // Copyright (c) 2012 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_EXTENSIONS_BROWSER_ACTION_BUTTON_H_
 #define CHROME_BROWSER_UI_COCOA_EXTENSIONS_BROWSER_ACTION_BUTTON_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
 
 #import "base/mac/scoped_nsobject.h"
 #import "chrome/browser/ui/cocoa/image_button_cell.h"
 #import "chrome/browser/ui/cocoa/toolbar/toolbar_button_cocoa.h"
 
-class Browser;
 @class BrowserActionsController;
 @class MenuController;
 class ToolbarActionViewController;
 class ToolbarActionViewDelegateBridge;
 
 // Fired on each drag event while the user is moving the button.
 extern NSString* const kBrowserActionButtonDraggingNotification;
 // Fired when the user drops the button.
 extern NSString* const kBrowserActionButtonDragEndNotification;
 
@@ skipping 82 matching lines @@
   // The controller for the browser actions bar that owns the button. Weak.
   BrowserActionsController* browserActionsController_;
 }
 
 @property(assign, nonatomic)
     BrowserActionsController* browserActionsController;
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_EXTENSIONS_BROWSER_ACTION_BUTTON_H_