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

chrome/browser/search_engines/template_url_prepopulate_data.h

Index: chrome/browser/search_engines/template_url_prepopulate_data.h
diff --git a/chrome/browser/search_engines/template_url_prepopulate_data.h b/chrome/browser/search_engines/template_url_prepopulate_data.h
index 5591fc9259e2fd03e686e6ac15889db6501ee4a3..2bf0b19cff7cba3bcce1c4088f736d51577ac6f2 100644
--- a/chrome/browser/search_engines/template_url_prepopulate_data.h
+++ b/chrome/browser/search_engines/template_url_prepopulate_data.h
@@ -11,6 +11,7 @@
 
 class GURL;
 class PrefService;
+class Profile;
 class TemplateURL;
 
 namespace TemplateURLPrepopulateData {
@@ -37,7 +38,7 @@ TemplateURL* GetPrepopulatedDefaultSearch(PrefService* prefs);
 // Returns a TemplateURL from the prepopulated data which has the same origin
 // as the given url.  The caller is responsible for deleting the returned
 // TemplateURL.
-TemplateURL* GetEngineForOrigin(PrefService* prefs, const GURL& url_to_find);
+TemplateURL* GetEngineForOrigin(Profile* profile, const GURL& url_to_find);
 
 // Returns search engine logo for URLs known to have a search engine logo.
 int GetSearchEngineLogo(const GURL& url_to_find);