Build correct URL for cacheinvalidation endpoint.

sync/notifier/gcm_network_channel.h

Index: sync/notifier/gcm_network_channel.h
diff --git a/sync/notifier/gcm_network_channel.h b/sync/notifier/gcm_network_channel.h
index b2e541d9867c1a29f937148e45d8617f39138719..7759c12c4b1d71f378e6ae71493990da2f177340 100644
--- a/sync/notifier/gcm_network_channel.h
+++ b/sync/notifier/gcm_network_channel.h
@@ -48,13 +48,14 @@ class SYNC_EXPORT_PRIVATE GCMNetworkChannel
       const net::BackoffEntry::Policy* policy);
 
  private:
+  friend class GCMNetworkChannelTest;
   void Register();
   void OnRegisterComplete(const std::string& registration_id,
                           gcm::GCMClient::Result result);
   void RequestAccessToken();
   void OnGetTokenComplete(const GoogleServiceAuthError& error,
                           const std::string& token);
-  GURL BuildUrl();
+  static GURL BuildUrl(const std::string& registration_id);
 
   scoped_refptr<net::URLRequestContextGetter> request_context_getter_;
   scoped_ptr<GCMNetworkChannelDelegate> delegate_;