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..9d410a4e7ca7eca932d3ca863ee2bf9dcda322e4 100644
--- a/chrome/browser/ui/browser_instant_controller.cc
+++ b/chrome/browser/ui/browser_instant_controller.cc
@@ -46,7 +46,20 @@ 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 kInstantExtendedEnabled still has a default value, and the
+  // intent is for it to have the same starting value as whatever
+  // kInstantEnabled has, then we set it to the value of
+  // kInstantEnabled.
+  if (search::GetInstantExtendedDefaultSetting() ==
+      search::INSTANT_USE_EXISTING &&
+      prefs->FindPref(prefs::kInstantExtendedEnabled)->IsDefaultValue()) {
+    prefs->SetBoolean(prefs::kInstantExtendedEnabled,
+                      prefs->GetBoolean(prefs::kInstantEnabled));

[Mattias Nissler (ping if slow), 2013/02/22 17:07:56]

After all the discussion, I don't think copying the value is a good idea, given
that he existing value may come from policy or whatever and coping that doesn't
reflect what we want.

Can we:

(1) not copy pref values

(2) Change IsInstantEnabled below to look at both prefs and use the appropriate
one as determined by 

(search::GetInstantExtendedDefaultSetting() == search::INSTANT_USE_EXISTING &&
prefs->FindPref(prefs::kInstantExtendedEnabled)->IsDefaultValue())

(3) wire the pref registrar to both pref names so we're sure to pick up changes
no matter which pref changes?

+  }
+
+  profile_pref_registrar_.Init(prefs);
   profile_pref_registrar_.Add(
       GetInstantPrefName(profile()),
       base::Bind(&BrowserInstantController::ResetInstant,
@@ -76,9 +89,7 @@ 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 +100,10 @@ void BrowserInstantController::RegisterUserPrefs(
     case search::INSTANT_DEFAULT_ON:
       instant_extended_default = true;
       break;
+    // In the INSTANT_USE_EXISTING case, the kInstantExtendedEnabled
+    // preference, if it still has a default value, is set to the
+    // value of kInstantEnabled in the constructor of this class.
     case search::INSTANT_USE_EXISTING:
-      instant_extended_default = prefs->GetBoolean(prefs::kInstantEnabled);
-      break;
     case search::INSTANT_DEFAULT_OFF:
       instant_extended_default = false;
       break;