Aura-Mus: Enable Surface Synchronization behind flag

ui/aura/mus/client_surface_embedder.h

Index: ui/aura/mus/client_surface_embedder.h
diff --git a/ui/aura/mus/client_surface_embedder.h b/ui/aura/mus/client_surface_embedder.h
index 6fe1f244ae702bc4276087a26eda6a5edfd21e7f..ef2f73575ea8e694781ad54018966ab77825b6cc 100644
--- a/ui/aura/mus/client_surface_embedder.h
+++ b/ui/aura/mus/client_surface_embedder.h
@@ -30,6 +30,8 @@ class ClientSurfaceEmbedder {
   // on the provided |surface_info|.
   void SetPrimarySurfaceInfo(const cc::SurfaceInfo& surface_info);
 
+  void SetFallbackSurfaceInfo(const cc::SurfaceInfo& surface_info);

[sadrul, 2017/03/31 01:26:20]

Does the clip-layer apply here? Are there restrictions on the fallback surface?
(e.g. does its size have to match the size of the primary surface, and so on)

[Fady Samuel, 2017/03/31 01:57:43]

The clip layer is explicitly NOT updated. I've explained as much in a comment.

+
  private:
   // The window which embeds the client.
   Window* window_;