Do not count image search results towards the GWS metric.

chrome/browser/prerender/prerender_manager.cc

 // 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.
 
 #include "chrome/browser/prerender/prerender_manager.h"
 
 #include <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
@@ skipping 281 matching lines @@
 }
 
 bool PrerenderManager::AddPrerender(
     Origin origin,
     const std::pair<int, int>& child_route_id_pair,
     const GURL& url_arg,
     const GURL& referrer) {
   DCHECK(CalledOnValidThread());
 
   if (origin == ORIGIN_LINK_REL_PRERENDER &&
-      StartsWithASCII(referrer.host(), std::string("www.google."), true)) {
+      StartsWithASCII(referrer.host(), std::string("www.google."), true) &&
+      !StartsWithASCII(referrer.path(), std::string("/imgres"), true)) {

[dominich, 2011/08/30 14:38:12]

As other Google properties use prerendering we will need this to scale better.
Instead of a negative match on the path, can we do a positive match:

StartsWithASCII(referrer.path(), std::string("/search"), true);

     origin = ORIGIN_GWS_PRERENDER;
   }
 
   histograms_->RecordPrerender(origin, url_arg);
 
   // If the referring page is prerendering, defer the prerender.
   if (FindPrerenderContentsForChildRouteIdPair(child_route_id_pair) !=
           prerender_list_.end()) {
     AddPendingPrerender(origin, child_route_id_pair, url_arg, referrer);
     return true;
@@ skipping 718 matching lines @@
   DeletePendingDeleteEntries();
 }
 
 void PrerenderManager::RecordFinalStatus(Origin origin,
                                          uint8 experiment_id,
                                          FinalStatus final_status) const {
   histograms_->RecordFinalStatus(origin, experiment_id, final_status);
 }
 
 }  // namespace prerender