Order the GL overlays above windows if possible.

content/browser/renderer_host/render_widget_host_view_mac.h

Index: content/browser/renderer_host/render_widget_host_view_mac.h
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.h b/content/browser/renderer_host/render_widget_host_view_mac.h
index 03c2d5e06f8f138be5524f1efadab28b1af36a9a..c1ab8636dbca08e484ceb934d1e0e0e2b16a076e 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.h
+++ b/content/browser/renderer_host/render_widget_host_view_mac.h
@@ -199,6 +199,7 @@ class RenderWidgetHostViewMac : public RenderWidgetHostViewBase {
   RenderWidgetHostViewCocoa* cocoa_view() const { return cocoa_view_; }
 
   void SetDelegate(NSObject<RenderWidgetHostViewMacDelegate>* delegate);
+  void SetAllowOverlappingViews(bool overlapping);
 
   // RenderWidgetHostView implementation.
   virtual void InitAsChild(gfx::NativeView parent_view) OVERRIDE;
@@ -425,6 +426,9 @@ class RenderWidgetHostViewMac : public RenderWidgetHostViewBase {
 
   scoped_ptr<CompositingIOSurfaceMac> compositing_iosurface_;
 
+  // Whether to allow overlapping views.
+  bool allow_overlapping_views_;
+
   NSWindow* pepper_fullscreen_window() const {
     return pepper_fullscreen_window_;
   }