Smooth Tab Switching on aura.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 737401c5c43a9f66c0f6d38bf2b4a6446db86db1..4a98e5d30e8e8deb5529ee892f28f5e2b192f6c4 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -22,6 +22,10 @@
 #include "ui/gfx/rect.h"
 #include "webkit/glue/webcursor.h"
 
+namespace aura {
+class CompositorLock;
+}
+
 namespace content {
 class RenderWidgetHostImpl;
 class RenderWidgetHostView;
@@ -307,6 +311,9 @@ class RenderWidgetHostViewAura
   // These locks are the ones waiting for a frame to be drawn.
   std::vector<linked_ptr<ResizeLock> > locks_pending_draw_;
 
+  // This lock is for waiting for a front surface to become available to draw.
+  scoped_refptr<aura::CompositorLock> released_front_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAura);
 };