Fix a crash in FullscreenExitBubbleController when the user clicks the "Exit full screen" button.

chrome/browser/ui/cocoa/browser_window_controller.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_BROWSER_WINDOW_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_BROWSER_WINDOW_CONTROLLER_H_
 #pragma once
 
 // A class acting as the Objective-C controller for the Browser
 // object. Handles interactions between Cocoa and the cross-platform
@@ skipping 442 matching lines @@
 - (NSWindow*)createFullscreenWindow;
 
 // Resets any saved state about window growth (due to showing the bookmark bar
 // or the download shelf), so that future shrinking will occur from the bottom.
 - (void)resetWindowGrowthState;
 
 // Computes by how far in each direction, horizontal and vertical, the
 // |source| rect doesn't fit into |target|.
 - (NSSize)overflowFrom:(NSRect)source
                     to:(NSRect)target;
+
+// The fullscreen exit bubble controller, or nil if the bubble isn't showing.
+- (FullscreenExitBubbleController*)fullscreenExitBubbleController;
 @end  // @interface BrowserWindowController (TestingAPI)
 
 
 #endif  // CHROME_BROWSER_UI_COCOA_BROWSER_WINDOW_CONTROLLER_H_