Remove the sender_id from the Push API code path.

content/renderer/push_messaging_dispatcher.h

Index: content/renderer/push_messaging_dispatcher.h
diff --git a/content/renderer/push_messaging_dispatcher.h b/content/renderer/push_messaging_dispatcher.h
index 080510fc6c63edd7c67c90ea8791d93fdae0c466..de9f8c97a71ab20b93f620597ea5688e0bb0588d 100644
--- a/content/renderer/push_messaging_dispatcher.h
+++ b/content/renderer/push_messaging_dispatcher.h
@@ -38,13 +38,16 @@ class PushMessagingDispatcher : public RenderFrameObserver,
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // WebPushClient implementation.
+  // TODO(peter): Remove this signature of registerPushMessaging.
   virtual void registerPushMessaging(
       const blink::WebString& sender_id,
       blink::WebPushRegistrationCallbacks* callbacks,
       blink::WebServiceWorkerProvider* service_worker_provider);
+  virtual void registerPushMessaging(
+      blink::WebPushRegistrationCallbacks* callbacks,
+      blink::WebServiceWorkerProvider* service_worker_provider);
 
-  void DoRegister(const std::string& sender_id,
-                  blink::WebPushRegistrationCallbacks* callbacks,
+  void DoRegister(blink::WebPushRegistrationCallbacks* callbacks,
                   blink::WebServiceWorkerProvider* service_worker_provider,
                   const Manifest& manifest);