Order the GL overlays above windows if possible.

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
diff --git a/content/browser/web_contents/web_contents_view_mac.mm b/content/browser/web_contents/web_contents_view_mac.mm
index 777cc270632f8b02dc245e13a2c2476325f4c117..9d49e39c96089142310a1b8a1fae9fbde6645b69 100644
--- a/content/browser/web_contents/web_contents_view_mac.mm
+++ b/content/browser/web_contents/web_contents_view_mac.mm
@@ -79,7 +79,8 @@ WebContentsView* CreateWebContentsView(
 WebContentsViewMac::WebContentsViewMac(WebContentsImpl* web_contents,
                                        WebContentsViewDelegate* delegate)
     : web_contents_(web_contents),
-      delegate_(delegate) {
+      delegate_(delegate),
+      allow_overlapping_views_(false) {
 }
 
 WebContentsViewMac::~WebContentsViewMac() {
@@ -116,6 +117,7 @@ RenderWidgetHostView* WebContentsViewMac::CreateViewForWidget(
         delegate()->CreateRenderWidgetHostViewDelegate(render_widget_host);
     view->SetDelegate(rw_delegate);
   }
+  view->SetAllowOverlappingViews(allow_overlapping_views_);
 
   // Fancy layout comes later; for now just make it our size and resize it
   // with us. In case there are other siblings of the content area, we want
@@ -334,6 +336,15 @@ gfx::Rect WebContentsViewMac::GetViewBounds() const {
   return gfx::Rect();
 }
 
+void WebContentsViewMac::SetAllowOverlappingViews(bool overlapping) {
+  if (allow_overlapping_views_ != overlapping) {
+    allow_overlapping_views_ = overlapping;
+    RenderWidgetHostViewMac* view = static_cast<RenderWidgetHostViewMac*>(
+        web_contents_->GetRenderWidgetHostView());
+    view->SetAllowOverlappingViews(allow_overlapping_views_);
+  }
+}
+
 void WebContentsViewMac::CloseTab() {
   web_contents_->Close(web_contents_->GetRenderViewHost());
 }