Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/custom_frame_view.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_CUSTOM_FRAME_VIEW_H_
+#define CHROME_BROWSER_UI_COCOA_CUSTOM_FRAME_VIEW_H_
+
 #import <Cocoa/Cocoa.h>
 
 // CustomFrameView is a class whose methods we swizzle into NSGrayFrame
 // on 10.7 and below, or NSThemeFrame on 10.8 and above, so that we can
 // support custom frame drawing.
 // This class is never to be instantiated on its own.
 
 @interface NSView (CustomFrameView)
 
 // Returns where the fullscreen button's origin should be positioned in window
 // coordinates.
 // We swizzle NSThemeFrame's implementation to center it vertically in the
 // tabstrip (if there is a tabstrip), and to shift it to the left of the
 // old-style avatar icon if necessary.
 - (NSPoint)_fullScreenButtonOrigin;
 
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_CUSTOM_FRAME_VIEW_H_