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 701 matching lines @@
   if (request_->response_info().network_accessed) {
     UMA_HISTOGRAM_ENUMERATION("Net.HttpResponseInfo.ConnectionInfo",
                               request_->response_info().connection_info,
                               net::HttpResponseInfo::NUM_OF_CONNECTION_INFOS);
   }
 
   ResourceRequestInfoImpl* info = GetRequestInfo();
 
   if (info->GetResourceType() == RESOURCE_TYPE_PREFETCH) {
     PrefetchStatus status = STATUS_UNDEFINED;
     TimeDelta total_time = base::TimeTicks::Now() - request_->creation_time();

[gavinp, 2016/04/25 15:39:05]

Since this is defined on both sides of the if(), should it be moved up above it?

[jkarlin, 2016/04/25 15:46:14]

Either case is likely to be rare (if prefetch or unused_since_prefetch) so it
seemed better to wait until necessary. I could go either way, let me know which
you prefer.

[gavinp, 2016/04/25 15:47:47]

Oh, you're right. I hadn't paid enough attention to see that it was an "else
if". Yes, duplicate it in each section.

 
     switch (request_->status().status()) {
       case net::URLRequestStatus::SUCCESS:
         if (request_->was_cached()) {
           status = STATUS_SUCCESS_FROM_CACHE;
           UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeSpentPrefetchingFromCache",
                               total_time);
         } else {
           status = STATUS_SUCCESS_FROM_NETWORK;
           UMA_HISTOGRAM_TIMES("Net.Prefetch.TimeSpentPrefetchingFromNetwork",
                               total_time);
         }
         break;
       case net::URLRequestStatus::CANCELED:
         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