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

chrome/browser/ui/views/default_search_view.h

Index: chrome/browser/ui/views/default_search_view.h
diff --git a/chrome/browser/ui/views/default_search_view.h b/chrome/browser/ui/views/default_search_view.h
index f055b4e166e8a9ffb937b65bff4adc7134201b4f..7ec827c64c97874dd9c12d92e2e69e729cdb02c2 100644
--- a/chrome/browser/ui/views/default_search_view.h
+++ b/chrome/browser/ui/views/default_search_view.h
@@ -16,7 +16,7 @@
 #include "chrome/browser/ui/gtk/constrained_window_gtk.h"
 #endif
 
-class PrefService;
+class Profile;
 class TabContents;
 class TemplateURL;
 class TemplateURLService;
@@ -72,7 +72,7 @@ class DefaultSearchView
                     TemplateURLService* template_url_service);
 
   // Initializes the labels and controls in the view.
-  void SetupControls(PrefService* prefs);
+  void SetupControls(Profile* prefs);
 
   // Image of browser search box with grey background and bubble arrow.
   views::ImageView* background_image_;