Eliminate spurious request cancelations

content/browser/loader/resource_dispatcher_host_impl.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.
 
 // See http://dev.chromium.org/developers/design-documents/multi-process-resource-loading
 
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 
 #include <stddef.h>
 
@@ skipping 1744 matching lines @@
 // CancelRequest methods in this file, which also tear down the loader.
 void ResourceDispatcherHostImpl::OnCancelRequest(int request_id) {
   int child_id = filter_->child_id();
 
   // When the old renderer dies, it sends a message to us to cancel its
   // requests.
   if (IsTransferredNavigation(GlobalRequestID(child_id, request_id)))
     return;
 
   ResourceLoader* loader = GetLoader(child_id, request_id);
-  if (!loader) {
-    // We probably want to remove this warning eventually, but I wanted to be
-    // able to notice when this happens during initial development since it
-    // should be rare and may indicate a bug.
-    DVLOG(1) << "Canceling a request that wasn't found";
+
+  // It is possible that the request has been completed and removed from the
+  // loader queue but the client has not processed the request completed message
+  // before issuing a cancel. This happens frequently for beacons which are
+  // canceled in the response received handler.
+  if (!loader)
     return;
-  }
 
   loader->CancelRequest(true);
 }
 
 ResourceRequestInfoImpl* ResourceDispatcherHostImpl::CreateRequestInfo(
     int child_id,
     int render_view_route_id,
     int render_frame_route_id,
     bool download,
     ResourceContext* context) {
@@ skipping 923 matching lines @@
         request_info->GetRouteID(), is_content_initiated, true, &throttles);
     if (!throttles.empty()) {
       handler.reset(new ThrottlingResourceHandler(std::move(handler), request,
                                                   std::move(throttles)));
     }
   }
   return handler;
 }
 
 }  // namespace content