Do not count image search results towards the GWS metric.

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
===================================================================
--- chrome/browser/prerender/prerender_manager.cc	(revision 98734)
+++ chrome/browser/prerender/prerender_manager.cc	(working copy)
@@ -299,7 +299,8 @@
   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;
   }