Add a bare-bones extension shelf that displays extension items on OS X.

chrome/browser/cocoa/status_bubble_mac.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.
 
 #ifndef CHROME_BROWSER_COCOA_STATUS_BUBBLE_MAC_H_
 #define CHROME_BROWSER_COCOA_STATUS_BUBBLE_MAC_H_
 
 #include <string>
 
 #import <Cocoa/Cocoa.h>
@@ skipping 37 matching lines @@
   NSWindow* window_;
 
   // The status text we want to display when there are no URLs to display.
   NSString* status_text_;
 
   // The url we want to display when there is no status text to display.
   NSString* url_text_;
 
   // How vertically offset the bubble is from its root position.
   int offset_;
-
-  // Is the download shelf visible.
-  bool is_download_shelf_visible_;
 };
 
 // Delegate interface that allows the StatusBubble to query its delegate about
 // the vertical offset (if any) that should be applied to the StatusBubble's
 // position.
 @interface NSObject(StatusBubbleDelegate)
 - (float)verticalOffsetForStatusBubble;
 @end
 
 #endif  // #ifndef CHROME_BROWSER_COCOA_STATUS_BUBBLE_MAC_H_