Order the GL overlays above windows if possible.

content/public/browser/web_contents_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 CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_VIEW_H_
 #define CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_VIEW_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 99 matching lines @@
   // If we close the tab while a UI control is in an event-tracking
   // loop, the control may message freed objects and crash.
   // WebContents::Close() calls IsEventTracking(), and if it returns
   // true CloseTabAfterEventTracking() is called and the close is not
   // completed.
   virtual bool IsEventTracking() const = 0;
   virtual void CloseTabAfterEventTracking() = 0;
 
   // Get the bounds of the View, relative to the parent.
   virtual gfx::Rect GetViewBounds() const = 0;
+
+#if defined(OS_MACOSX)
+  // The web contents view assumes that its view will never be overlapped by
+  // another view (either partially or fully). This allows it to perform
+  // optimizations. If the view is in a view hierarchy where it might be
+  // overlapped by another view, notify the view by calling this with |true|
+  // before it draws for the first time. After the first draw, do not change
+  // this setting.
+  virtual void SetAllowOverlappingViews(bool overlapping) = 0;
+#endif
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_WEB_CONTENTS_VIEW_H_