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

chrome/browser/ui/browser_instant_controller.cc

Index: chrome/browser/ui/browser_instant_controller.cc
diff --git a/chrome/browser/ui/browser_instant_controller.cc b/chrome/browser/ui/browser_instant_controller.cc
index 582ae88a9009ee2429c033d94ebfc861278d625f..d3651a67c455eb038c00dc5438545ecc6b739aaa 100644
--- a/chrome/browser/ui/browser_instant_controller.cc
+++ b/chrome/browser/ui/browser_instant_controller.cc
@@ -46,7 +46,16 @@ BrowserInstantController::BrowserInstantController(Browser* browser)
                chrome::search::IsInstantExtendedAPIEnabled(profile())),
       instant_unload_handler_(browser),
       initialized_theme_info_(false) {
-  profile_pref_registrar_.Init(profile()->GetPrefs());
+  PrefService* prefs = profile()->GetPrefs();
+
+  if (search::GetInstantExtendedDefaultSetting() ==
+      search::INSTANT_USE_EXISTING) {
+    prefs->SetDefaultPrefValue(prefs::kInstantExtendedEnabled,
+                               Value::CreateBooleanValue(
+                                   prefs->GetBoolean(prefs::kInstantEnabled)));
+  }
+
+  profile_pref_registrar_.Init(prefs);
   profile_pref_registrar_.Add(
       GetInstantPrefName(profile()),
       base::Bind(&BrowserInstantController::ResetInstant,
@@ -76,9 +85,7 @@ bool BrowserInstantController::IsInstantEnabled(Profile* profile) {
 }
 
 void BrowserInstantController::RegisterUserPrefs(
-    PrefService* prefs,
     PrefRegistrySyncable* registry) {
-  // TODO(joi): Get rid of the need for PrefService param above.
   registry->RegisterBooleanPref(prefs::kInstantConfirmDialogShown, false,
                                 PrefRegistrySyncable::SYNCABLE_PREF);
   registry->RegisterBooleanPref(prefs::kInstantEnabled, false,
@@ -90,8 +97,8 @@ void BrowserInstantController::RegisterUserPrefs(
       instant_extended_default = true;
       break;
     case search::INSTANT_USE_EXISTING:
-      instant_extended_default = prefs->GetBoolean(prefs::kInstantEnabled);
-      break;
+      // Fall-through to false; the default gets reset in the
+      // BrowserInstantController constructor in this case.

[Mattias Nissler (ping if slow), 2013/02/27 10:50:52]

Maybe we can move all default setting to the ctor for simplicity now?

[Jói, 2013/02/27 16:30:56]

Done.

     case search::INSTANT_DEFAULT_OFF:
       instant_extended_default = false;
       break;