Order the GL overlays above windows if possible.

content/browser/renderer_host/compositing_iosurface_mac.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_BROWSER_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H
 #define CONTENT_BROWSER_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H
 
 #import <Cocoa/Cocoa.h>
 #import <QuartzCore/CVDisplayLink.h>
 #include <QuartzCore/QuartzCore.h>
@@ skipping 14 matching lines @@
 class Rect;
 }
 
 namespace content {
 
 // This class manages an OpenGL context and IOSurface for the accelerated
 // compositing code path. The GL context is attached to
 // RenderWidgetHostViewCocoa for blitting the IOSurface.
 class CompositingIOSurfaceMac {
  public:
-  // Returns NULL if IOSurface support is missing or GL APIs fail.
-  static CompositingIOSurfaceMac* Create();
+  // Passed to Create() to specify the ordering of the surface relative to the
+  // containing window.
+  enum SurfaceOrder {
+    SURFACE_ORDER_ABOVE_WINDOW,
+    SURFACE_ORDER_BELOW_WINDOW
+  };
+
+  // Returns NULL if IOSurface support is missing or GL APIs fail. Specify in
+  // |order| the desired ordering relationship of the surface to the containing
+  // window.
+  static CompositingIOSurfaceMac* Create(SurfaceOrder order);
   ~CompositingIOSurfaceMac();
 
   // Set IOSurface that will be drawn on the next NSView drawRect.
   void SetIOSurface(uint64 io_surface_handle,
                     const gfx::Size& size);
 
   // Blit the IOSurface at the upper-left corner of the |view|. If |view| window
   // size is larger than the IOSurface, the remaining right and bottom edges
   // will be white. |scaleFactor| is 1 in normal views, 2 in HiDPI views.
   void DrawIOSurface(NSView* view, float scale_factor);
@@ skipping 226 matching lines @@
 
   // Vsync timing data.
   base::TimeTicks vsync_timebase_;
   uint32 vsync_interval_numerator_;
   uint32 vsync_interval_denominator_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_ACCELERATED_COMPOSITING_VIEW_MAC_H