Avoid double calling OnResponseStarted from BufferedResourceHandler

content/browser/download/download_resource_handler.cc

 // 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.
 
 #include "content/browser/download/download_resource_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/logging.h"
@@ skipping 54 matching lines @@
       render_view_id_(render_view_id),
       content_length_(0),
       download_file_manager_(download_file_manager),
       request_(request),
       started_cb_(started_cb),
       save_info_(save_info),
       buffer_(new content::DownloadBuffer),
       last_buffer_size_(0),
       bytes_read_(0),
       pause_count_(0),
-      was_deferred_(false) {
+      was_deferred_(false),
+      on_response_started_called_(false) {
   download_stats::RecordDownloadCount(download_stats::UNTHROTTLED_COUNT);
 }
 
 bool DownloadResourceHandler::OnUploadProgress(int request_id,
                                                uint64 position,
                                                uint64 size) {
   return true;
 }
 
 // Not needed, as this event handler ought to be the final resource.
 bool DownloadResourceHandler::OnRequestRedirected(
     int request_id,
     const GURL& url,
     content::ResourceResponse* response,
     bool* defer) {
   return true;
 }
 
 // Send the download creation information to the download thread.
 bool DownloadResourceHandler::OnResponseStarted(
     int request_id,
     content::ResourceResponse* response,
     bool* defer) {
+  // There can be only one (call)
+  DCHECK(!on_response_started_called_);
+  on_response_started_called_ = true;
+
   VLOG(20) << __FUNCTION__ << "()" << DebugString()
            << " request_id = " << request_id;
   download_start_time_ = base::TimeTicks::Now();
 
   // If it's a download, we don't want to poison the cache with it.
   request_->StopCaching();
 
   std::string content_disposition;
   request_->GetResponseHeaderByName("content-disposition",
                                     &content_disposition);
@@ skipping 386 matching lines @@
   if (download_id_ == DownloadId::Invalid())
     return;
   if (buffer_.get() && (buffer_->size() > kLoadsToWrite))
     return;
 
   was_deferred_ = false;
   ResourceDispatcherHostImpl::Get()->ResumeDeferredRequest(
       global_id_.child_id,
       global_id_.request_id);
 }