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

chrome/browser/search_engines/search_provider_install_data.h

Index: chrome/browser/search_engines/search_provider_install_data.h
diff --git a/chrome/browser/search_engines/search_provider_install_data.h b/chrome/browser/search_engines/search_provider_install_data.h
index 191615c76a3209b18691f56260e556f7e06897b3..8f860e846f88732e41180d26740871c419f100e8 100644
--- a/chrome/browser/search_engines/search_provider_install_data.h
+++ b/chrome/browser/search_engines/search_provider_install_data.h
@@ -18,6 +18,7 @@
 
 class GURL;
 class NotificationSource;
+class Profile;
 class SearchHostToURLsMap;
 class Task;
 class TemplateURL;
@@ -46,7 +47,8 @@ class SearchProviderInstallData : public WebDataServiceConsumer,
   // that notification occurs. It doesn't matter.)
   SearchProviderInstallData(WebDataService* web_service,
                             int ui_death_notification,
-                            const NotificationSource& ui_death_source);
+                            const NotificationSource& ui_death_source,
+                            Profile* profile);
   virtual ~SearchProviderInstallData();
 
   // Use to determine when the search provider information is loaded. The