Replace more ObserverList with base::ObserverList.

content/browser/service_worker/embedded_worker_instance.h

Index: content/browser/service_worker/embedded_worker_instance.h
diff --git a/content/browser/service_worker/embedded_worker_instance.h b/content/browser/service_worker/embedded_worker_instance.h
index aebbe383cccb76f6100a66d5978d14089f397929..309c2ddf7a33969099f9723ccf525ffe16a4bea5 100644
--- a/content/browser/service_worker/embedded_worker_instance.h
+++ b/content/browser/service_worker/embedded_worker_instance.h
@@ -143,7 +143,7 @@ class CONTENT_EXPORT EmbeddedWorkerInstance {
   static std::string StartingPhaseToString(StartingPhase phase);
 
  private:
-  typedef ObserverList<Listener> ListenerList;
+  typedef base::ObserverList<Listener> ListenerList;
   class DevToolsProxy;
   friend class EmbeddedWorkerRegistry;
   FRIEND_TEST_ALL_PREFIXES(EmbeddedWorkerInstanceTest, StartAndStop);