Mustash: Ensure surfaces submitted to Mus by WM and embedders contain Surfaces with embeded content.

ui/aura/mus/window_port_mus.cc

Index: ui/aura/mus/window_port_mus.cc
diff --git a/ui/aura/mus/window_port_mus.cc b/ui/aura/mus/window_port_mus.cc
index 305fcfc16b603722063e646d1b5277d4fe8074ba..da1ae155fc2cc98e5f27764f39a5c79bde01a128 100644
--- a/ui/aura/mus/window_port_mus.cc
+++ b/ui/aura/mus/window_port_mus.cc
@@ -7,6 +7,7 @@
 #include "base/memory/ptr_util.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/transient_window_client.h"
+#include "ui/aura/mus/client_surface_embedder.h"
 #include "ui/aura/mus/property_converter.h"
 #include "ui/aura/mus/surface_id_handler.h"
 #include "ui/aura/mus/window_tree_client.h"
@@ -255,10 +256,22 @@ void WindowPortMus::SetSurfaceInfoFromServer(
     }
   }
   WindowPortMus* parent = Get(window_->parent());
+  // TODO(mfomitchev): This is unused. We probably don't need this.
   if (parent && parent->surface_id_handler_) {
     parent->surface_id_handler_->OnChildWindowSurfaceChanged(window_,
                                                              surface_info);
   }
+
+  // The fact that SetSurfaceIdFromServer was called means that this window
+  // corresponds to an embedded client.
+  if (!client_surface_embedder && surface_info.id().is_valid())
+    client_surface_embedder = base::MakeUnique<ClientSurfaceEmbedder>(window_);
+
+  if (surface_info.id().is_valid())
+    client_surface_embedder->UpdateSurface(surface_info);
+  else
+    client_surface_embedder.reset();
+
   surface_info_ = surface_info;
 }