Fix prefs registration for 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..af34c19eee01a5356036294174ebdee92c299dec 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();
+
+  // kInstantExtendedEnabled takes the value of kInstantEnabled in this case.
+  if (search::GetInstantExtendedDefaultSetting() ==
+      search::INSTANT_USE_EXISTING) {
+    prefs->SetBoolean(prefs::kInstantExtendedEnabled,
+                      prefs->GetBoolean(prefs::kInstantEnabled));

[Mattias Nissler (ping if slow), 2013/02/22 13:06:16]

Note this is a change in semantics, not sure whether that's a good idea. I'd
rather change the code consuming kInstantExtendedEnabled to check for
IsDefaultValue() and if so, use the value of 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,
@@ -89,9 +96,7 @@ void BrowserInstantController::RegisterUserPrefs(
     case search::INSTANT_DEFAULT_ON:
       instant_extended_default = true;
       break;
-    case search::INSTANT_USE_EXISTING:
-      instant_extended_default = prefs->GetBoolean(prefs::kInstantEnabled);
-      break;
+    case search::INSTANT_USE_EXISTING:  // Initialized in constructor.

[robertshield, 2013/02/22 13:36:55]

It took me a few minutes to convince myself that this would work since it wasn't
obvious to me that the default value passed to RegisterBooleanPref wouldn't be
used if prefs->SetBoolean was called in the ctor. 

Please expand the comment to say that "Initialized in constructor." means that
the default value passed to RegisterBooleanPref will be ignored.

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