Hook embedded shell up to MojoShellConnection

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 45c7e3d9a8d8e5e6289bd159cde672878cb291ea..f90f7cfc97c719c66f32799adbd320fb454fe7d8 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -860,7 +860,9 @@ void RenderThreadImpl::Init() {
 #if defined(MOJO_SHELL_CLIENT)
   // We may not have a MojoShellConnection object in tests that directly
   // instantiate a RenderThreadImpl.
-  if (MojoShellConnection::Get())
+  if (MojoShellConnection::Get() &&
+      base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kUseMusInRenderer))
     CreateRenderWidgetWindowTreeClientFactory();
 #endif
 }