Revert 232766 "Refactor MediaStreamManager to never output real ..."

content/browser/renderer_host/media/media_stream_dispatcher_host.cc

Index: content/browser/renderer_host/media/media_stream_dispatcher_host.cc
===================================================================
--- content/browser/renderer_host/media/media_stream_dispatcher_host.cc	(revision 232998)
+++ content/browser/renderer_host/media/media_stream_dispatcher_host.cc	(working copy)
@@ -133,8 +133,12 @@
   const std::string& label = media_stream_manager_->GenerateStream(
       this, render_process_id_, render_view_id, page_request_id,
       components, security_origin);
-  CHECK(!label.empty());
-  StoreRequest(render_view_id, page_request_id, label);
+  if (label.empty()) {
+    Send(new MediaStreamMsg_StreamGenerationFailed(render_view_id,
+                                                   page_request_id));
+  } else {
+    StoreRequest(render_view_id, page_request_id, label);
+  }
 }
 
 void MediaStreamDispatcherHost::OnCancelGenerateStream(int render_view_id,