Enable media stream layout test with content_shell.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
===================================================================
--- content/renderer/render_view_impl.cc	(revision 191534)
+++ content/renderer/render_view_impl.cc	(working copy)
@@ -2676,7 +2676,15 @@
 
   const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
 #if defined(ENABLE_WEBRTC)
-  if (MediaStreamImpl::CheckMediaStream(url)) {
+  webkit_media::MediaStreamClient* media_stream_client =
+      GetContentClient()->renderer()->OverrideMediaStreamClient();
+  // For layout test with content_shell.

[jam, 2013/04/01 15:51:45]

nit: don't mention what an embedder might use this for.

+  if (media_stream_client) {
+    if (media_stream_client->IsMediaStream(url)) {
+      return new webkit_media::WebMediaPlayerMS(frame, client, AsWeakPtr(),
+          media_stream_client, new RenderMediaLog());
+    }
+  } else if (MediaStreamImpl::CheckMediaStream(url)) {
     EnsureMediaStreamImpl();
     return new webkit_media::WebMediaPlayerMS(
         frame, client, AsWeakPtr(), media_stream_impl_, new RenderMediaLog());
@@ -6313,6 +6321,11 @@
 }
 
 WebKit::WebUserMediaClient* RenderViewImpl::userMediaClient() {
+  WebKit::WebUserMediaClient* user_media_client =
+      GetContentClient()->renderer()->OverrideUserMediaClient();
+  if (user_media_client)
+    return user_media_client;
+
   EnsureMediaStreamImpl();
   return media_stream_impl_;
 }