Hook embedded shell up to MojoShellConnection

content/renderer/render_widget.cc

 // Copyright (c) 2012 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 "content/renderer/render_widget.h"
 
 #include <utility>
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
@@ skipping 687 matching lines @@
   // never get a request for a cc::OutputSurface.
   DCHECK(!compositor_never_visible_);
 
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   bool use_software = fallback;
   if (command_line.HasSwitch(switches::kDisableGpuCompositing))
     use_software = true;
 
 #if defined(MOJO_SHELL_CLIENT)
-  if (MojoShellConnection::Get() && !use_software) {
+  if (MojoShellConnection::Get() && !use_software &&
+      command_line.HasSwitch(switches::kUseMusInRenderer)) {
     RenderWidgetMusConnection* connection =
         RenderWidgetMusConnection::GetOrCreate(routing_id());
     return connection->CreateOutputSurface();
   }
 #endif
 
   scoped_refptr<GpuChannelHost> gpu_channel_host;
   if (!use_software) {
     CauseForGpuLaunch cause =
         CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE;
@@ skipping 1392 matching lines @@
   video_hole_frames_.RemoveObserver(frame);
 }
 #endif  // defined(VIDEO_HOLE)
 
 void RenderWidget::OnWaitNextFrameForTests(int routing_id) {
   QueueMessage(new ViewHostMsg_WaitForNextFrameForTests_ACK(routing_id),
                MESSAGE_DELIVERY_POLICY_WITH_VISUAL_STATE);
 }
 
 }  // namespace content