Add WorkerScriptLoaded message to support attaching DevTools while starting ServiceWorker.

content/browser/service_worker/embedded_worker_instance.cc

Index: content/browser/service_worker/embedded_worker_instance.cc
diff --git a/content/browser/service_worker/embedded_worker_instance.cc b/content/browser/service_worker/embedded_worker_instance.cc
index b56df25d360c32cb54c4346671cde192937df6b0..24d2a9529a9843eb6dbf7c36e44efeabd748dd4d 100644
--- a/content/browser/service_worker/embedded_worker_instance.cc
+++ b/content/browser/service_worker/embedded_worker_instance.cc
@@ -99,6 +99,13 @@ void EmbeddedWorkerInstance::RecordProcessId(
   }
 }
 
+void EmbeddedWorkerInstance::OnScriptLoaded() {
+  // TODO(horo): Implement this.
+}
+
+void EmbeddedWorkerInstance::OnScriptLoadFailed() {
+}
+
 void EmbeddedWorkerInstance::OnStarted(int thread_id) {
   // Stop is requested before OnStarted is sent back from the worker.
   if (status_ == STOPPING)