Introduce worker_devtools_agent_route_id for EmbeddedWorker.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index bf77203669d9854222d4918fe58e69e5c59d3cfc..94efe0fa9e36d0a31ebb97606b1fdeb6743f4843 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -461,11 +461,21 @@ void RenderProcessHostImpl::ShutDownInProcessRenderer() {
   }
 }
 
+// static
 void RenderProcessHostImpl::RegisterRendererMainThreadFactory(
     RendererMainThreadFactoryFunction create) {
   g_renderer_main_thread_factory = create;
 }
 
+// static
+int RenderProcessHostImpl::GetNextRoutingIDForProcess(int render_process_id) {
+  scoped_refptr<RenderWidgetHelper> helper(
+      RenderWidgetHelper::FromProcessHostID(render_process_id);
+  if (!helper)
+    return MSG_ROUTING_NONE;  // Maybe null in unittest.
+  return helper->GetNextRoutingID();
+}
+
 RenderProcessHostImpl::~RenderProcessHostImpl() {
 #ifndef NDEBUG
   DCHECK(is_self_deleted_)