Count successes of link rel=prefetch

content/browser/loader/resource_loader.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/loader/resource_loader.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/location.h"
@@ skipping 726 matching lines @@
         status = STATUS_CANCELED;
         UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeBeforeCancel", total_time);
         break;
       case net::URLRequestStatus::IO_PENDING:
       case net::URLRequestStatus::FAILED:
         status = STATUS_UNDEFINED;
         break;
     }
 
     UMA_HISTOGRAM_ENUMERATION("Net.Prefetch.Pattern", status, STATUS_MAX);
+  } else if (request_->response_info().unused_since_prefetch) {
+    TimeDelta total_time = base::TimeTicks::Now() - request_->creation_time();
+    UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeSpentOnPrefetchHit", total_time);
   }
 }
 
 }  // namespace content