Unregister GCMInvalidationBridge from GCMDriver when user signs out.

components/invalidation/gcm_invalidation_bridge.h

Index: components/invalidation/gcm_invalidation_bridge.h
diff --git a/components/invalidation/gcm_invalidation_bridge.h b/components/invalidation/gcm_invalidation_bridge.h
index 4f3e735078343f0ba590736592918b0b5c093daf..9f9fe42696996f062922e086176c2cb9bf1b55b6 100644
--- a/components/invalidation/gcm_invalidation_bridge.h
+++ b/components/invalidation/gcm_invalidation_bridge.h
@@ -86,6 +86,10 @@ class GCMInvalidationBridge : public gcm::GCMAppHandler,
       const std::string& registration_id,
       gcm::GCMClient::Result result);
 
+  void Unregister();
+
+  static void UnregisterFinishedNoOp(gcm::GCMClient::Result result);
+
  private:
   gcm::GCMDriver* const gcm_driver_;
   IdentityProvider* const identity_provider_;