Add a URL param to indicate group selection in Instant field trial.

chrome/browser/search_engines/search_host_to_urls_map.cc

Index: chrome/browser/search_engines/search_host_to_urls_map.cc
diff --git a/chrome/browser/search_engines/search_host_to_urls_map.cc b/chrome/browser/search_engines/search_host_to_urls_map.cc
index cb91724a0bb10044d9667a4f5c95fbb5f6644799..cb627aafb5241c52e8c9f0740bff71735a100691 100644
--- a/chrome/browser/search_engines/search_host_to_urls_map.cc
+++ b/chrome/browser/search_engines/search_host_to_urls_map.cc
@@ -34,7 +34,7 @@ void SearchHostToURLsMap::Add(const TemplateURL* template_url,
   DCHECK(template_url);
 
   const GURL url(TemplateURLService::GenerateSearchURLUsingTermsData(
-      template_url, search_terms_data));
+      NULL, template_url, search_terms_data));
   if (!url.is_valid() || !url.has_host())
     return;
 
@@ -45,7 +45,7 @@ void SearchHostToURLsMap::Remove(const TemplateURL* template_url) {
   DCHECK(initialized_);
   DCHECK(template_url);
 
-  const GURL url(TemplateURLService::GenerateSearchURL(template_url));
+  const GURL url(TemplateURLService::GenerateSearchURL(NULL, template_url));
   if (!url.is_valid() || !url.has_host())
     return;