Don't destroy a request while it is being processed

content/browser/renderer_host/resource_dispatcher_host.h

 // Copyright (c) 2011 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.
 
 // This is the browser side of the resource dispatcher, it receives requests
 // from the child process (i.e. [Renderer, Plugin, Worker]ProcessHost), and
 // dispatches them to URLRequests. It then forwards the messages from the
 // URLRequests back to the correct process for handling.
 //
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
@@ skipping 299 matching lines @@
   // no errors have occurred).
   bool CompleteRead(net::URLRequest*, int* bytes_read);
 
   // Internal function to finish handling the ResponseStarted message.  Returns
   // true on success.
   bool CompleteResponseStarted(net::URLRequest* request);
 
   // Helper function for regular and download requests.
   void BeginRequestInternal(net::URLRequest* request);
 
-  // Helper function that cancels |request|.
-  void CancelRequestInternal(net::URLRequest* request, bool from_renderer);
+  // Helper function that cancels |request|.  Returns whether the
+  // request was actually cancelled.  If a renderer cancels a request
+  // for a download, we ignore the cancellation.
+  bool CancelRequestInternal(net::URLRequest* request, bool from_renderer);
 
   // Helper function that inserts |request| into the resource queue.
   void InsertIntoResourceQueue(
       net::URLRequest* request,
       const ResourceDispatcherHostRequestInfo& request_info);
 
   // Updates the "cost" of outstanding requests for |process_unique_id|.
   // The "cost" approximates how many bytes are consumed by all the in-memory
   // data structures supporting this request (net::URLRequest object,
   // HttpNetworkTransaction, etc...).
@@ skipping 172 matching lines @@
 
   static bool is_prefetch_enabled_;
   typedef std::set<std::pair<int, int> > PrerenderChildRouteIdPairs;
   PrerenderChildRouteIdPairs prerender_child_route_pairs_;
 
 
   DISALLOW_COPY_AND_ASSIGN(ResourceDispatcherHost);
 };
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RESOURCE_DISPATCHER_HOST_H_