Aura-Mus: Avoid creating StubSurfaceReferenceFactory's on every surface ID change

ui/aura/mus/client_surface_embedder.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/mus/client_surface_embedder.h"
 
 #include "cc/surfaces/surface_reference_factory.h"
 #include "ui/aura/window.h"
 
 namespace aura {
@@ skipping 28 matching lines @@
   // The frame provided by the parent window->layer() needs to show through
   // the surface layer.
   surface_layer_->SetFillsBoundsOpaquely(false);
 
   window_->layer()->Add(surface_layer_.get());
 
   // Window's layer may contain content from this client (the embedder), e.g.
   // this is the case with window decorations provided by Window Manager.
   // This content should appear underneath the content of the embedded client.
   window_->layer()->StackAtTop(surface_layer_.get());
+  ref_factory_ = new StubSurfaceReferenceFactory();
 }
 
 ClientSurfaceEmbedder::~ClientSurfaceEmbedder() = default;
 
 void ClientSurfaceEmbedder::SetPrimarySurfaceInfo(
     const cc::SurfaceInfo& surface_info) {
-  surface_layer_->SetShowPrimarySurface(
-      surface_info, make_scoped_refptr(new StubSurfaceReferenceFactory));
+  surface_layer_->SetShowPrimarySurface(surface_info, ref_factory_);
   surface_layer_->SetBounds(gfx::Rect(window_->bounds().size()));
 }
 
 void ClientSurfaceEmbedder::SetFallbackSurfaceInfo(
     const cc::SurfaceInfo& surface_info) {
   surface_layer_->SetFallbackSurface(surface_info);
   UpdateSizeAndGutters();
 }
 
 void ClientSurfaceEmbedder::UpdateSizeAndGutters() {
@@ skipping 31 matching lines @@
     bottom_gutter_->SetBounds(
         gfx::Rect(0, fallback_surface_size.height(), width, height));
     window_->layer()->Add(bottom_gutter_.get());
   } else {
     bottom_gutter_.reset();
   }
   window_->layer()->StackAtTop(surface_layer_.get());
 }
 
 }  // namespace aura