GCM Engine: Split up reg/unreg UNKNOWN_ERROR to improve metrics

google_apis/gcm/engine/gcm_unregistration_request_handler.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GOOGLE_APIS_GCM_ENGINE_GCM_UNREGISTRATION_REQUEST_HANDLER_H_
 #define GOOGLE_APIS_GCM_ENGINE_GCM_UNREGISTRATION_REQUEST_HANDLER_H_
 
 #include "base/macros.h"
 #include "google_apis/gcm/engine/unregistration_request.h"
 
 namespace gcm {
 
 // Used to revoke the registration ID when unregister is called or the
 // application has been uninstalled.
 class GCM_EXPORT GCMUnregistrationRequestHandler :
     public UnregistrationRequest::CustomRequestHandler {
  public:
   GCMUnregistrationRequestHandler(const std::string& app_id);
   ~GCMUnregistrationRequestHandler() override;
 
   // UnregistrationRequest::CustomRequestHandler overrides:
   void BuildRequestBody(std::string* body) override;
   UnregistrationRequest::Status ParseResponse(
-      const net::URLFetcher* source) override;
+      const std::string& response) override;
   void ReportUMAs(UnregistrationRequest::Status status,
                   int retry_count,
                   base::TimeDelta complete_time) override;
 
  private:
   std::string app_id_;
 
   DISALLOW_COPY_AND_ASSIGN(GCMUnregistrationRequestHandler);
 };
 
 }  // namespace gcm
 
 #endif  // GOOGLE_APIS_GCM_ENGINE_GCM_UNREGISTRATION_REQUEST_HANDLER_H_