Avoid double calling OnResponseStarted from BufferedResourceHandler

content/browser/download/download_resource_handler.h

 // Copyright (c) 2012 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 CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 120 matching lines @@
   // The following are used to collect stats.
   base::TimeTicks download_start_time_;
   base::TimeTicks last_read_time_;
   size_t last_buffer_size_;
   int64 bytes_read_;
   std::string accept_ranges_;
 
   int pause_count_;
   bool was_deferred_;
 
+  // For DCHECKing
+  bool on_response_started_called_;
+
   static const int kReadBufSize = 32768;  // bytes
   static const int kThrottleTimeMs = 200;  // milliseconds
 
   DISALLOW_COPY_AND_ASSIGN(DownloadResourceHandler);
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_RESOURCE_HANDLER_H_