Push API: use (un)subscription instead of (un)registration

content/child/push_messaging/push_provider.h

Index: content/child/push_messaging/push_provider.h
diff --git a/content/child/push_messaging/push_provider.h b/content/child/push_messaging/push_provider.h
index 47442ae0230820edd0ba183b93ac7531a3347b8e..06728c220a855bd5019ebc0e28d42578b5d0134e 100644
--- a/content/child/push_messaging/push_provider.h
+++ b/content/child/push_messaging/push_provider.h
@@ -63,12 +63,12 @@ class PushProvider : public blink::WebPushProvider,
                PushDispatcher* push_dispatcher);
 
   // IPC message handlers.
-  void OnRegisterFromWorkerSuccess(int request_id,
+  void OnSubscribeFromWorkerSuccess(int request_id,
                                    const GURL& endpoint,
-                                   const std::string& registration_id);
-  void OnRegisterFromWorkerError(int request_id, PushRegistrationStatus status);
-  void OnUnregisterSuccess(int request_id, bool did_unregister);
-  void OnUnregisterError(int request_id,
+                                   const std::string& subscription_id);
+  void OnSubscribeFromWorkerError(int request_id, PushRegistrationStatus status);
+  void OnUnsubscribeSuccess(int request_id, bool did_unregister);
+  void OnUnsubscribeError(int request_id,
                          blink::WebPushError::ErrorType error_type,
                          const std::string& error_message);
   void OnGetRegistrationSuccess(int request_id,