Add ability to change default pref values, and use in BrowserInstantController.

chrome/browser/extensions/extension_service_unittest.cc

Index: chrome/browser/extensions/extension_service_unittest.cc
diff --git a/chrome/browser/extensions/extension_service_unittest.cc b/chrome/browser/extensions/extension_service_unittest.cc
index f096ffe4bed2960447eea947966163b05ea89762..7256ae9deea57bebec470af23de93c6bfe5601af 100644
--- a/chrome/browser/extensions/extension_service_unittest.cc
+++ b/chrome/browser/extensions/extension_service_unittest.cc
@@ -448,7 +448,7 @@ void ExtensionServiceTestBase::InitializeExtensionService(
       pref_file, loop_.message_loop_proxy());
   scoped_refptr<PrefRegistrySyncable> registry(new PrefRegistrySyncable);
   scoped_ptr<PrefServiceSyncable> prefs(builder.CreateSyncable(registry));
-  chrome::RegisterUserPrefs(prefs.get(), registry);
+  chrome::RegisterUserPrefs(registry);
   profile_builder.SetPrefService(prefs.Pass());
   profile_builder.SetPath(profile_path);
   profile_ = profile_builder.Build();