Add WorkerScriptLoaded message to support attaching DevTools while starting ServiceWorker.

content/renderer/service_worker/embedded_worker_context_client.cc

Index: content/renderer/service_worker/embedded_worker_context_client.cc
diff --git a/content/renderer/service_worker/embedded_worker_context_client.cc b/content/renderer/service_worker/embedded_worker_context_client.cc
index 688dd8590505d0f55abb46008e402500a5b1e30b..fc7bf9f2efa4b1eab5f2e2afdbfa341b2b9f7faa 100644
--- a/content/renderer/service_worker/embedded_worker_context_client.cc
+++ b/content/renderer/service_worker/embedded_worker_context_client.cc
@@ -146,6 +146,8 @@ void EmbeddedWorkerContextClient::workerContextStarted(
   g_worker_client_tls.Pointer()->Set(this);
   script_context_.reset(new ServiceWorkerScriptContext(this, proxy));
 
+  Send(new EmbeddedWorkerHostMsg_WorkerScriptLoaded(embedded_worker_id_));
+
   // Schedule a task to send back WorkerStarted asynchronously,
   // so that at the time we send it we can be sure that the worker
   // script has been evaluated and worker run loop has been started.