Add an option in language settings for activating the IME menu.

chrome/browser/chromeos/preferences.cc

Index: chrome/browser/chromeos/preferences.cc
diff --git a/chrome/browser/chromeos/preferences.cc b/chrome/browser/chromeos/preferences.cc
index e0810c895c9b77202ef28380db81f9bfe7af942f..da60c27f4829b35f01a2745a95f4d296c52d3613 100644
--- a/chrome/browser/chromeos/preferences.cc
+++ b/chrome/browser/chromeos/preferences.cc
@@ -285,6 +285,11 @@ void Preferences::RegisterProfilePrefs(
                                 true);
 
   registry->RegisterBooleanPref(prefs::kForceMaximizeOnFirstRun, false);
+
+  registry->RegisterBooleanPref(prefs::kLangugaeImeMenuFlagEnabled,

[michaelpg, 2016/01/04 16:37:36]

why is the flag also preference? do any other flags do this?

the pref isn't actually set anywhere, further suggesting we don't need it.

[Azure Wei, 2016/01/05 06:48:03]

This preference was used in language_options.js, it has been changed with
loadTimeData now.

+                                chromeos::switches::ImeMenuEnabled());
+
+  registry->RegisterBooleanPref(prefs::kLangugaeImeMenuActivated, false);
 }
 
 void Preferences::InitUserPrefs(syncable_prefs::PrefServiceSyncable* prefs) {
@@ -317,6 +322,7 @@ void Preferences::InitUserPrefs(syncable_prefs::PrefServiceSyncable* prefs) {
                              prefs, callback);
   previous_input_method_.Init(prefs::kLanguagePreviousInputMethod,
                               prefs, callback);
+  ime_menu_activated_.Init(prefs::kLangugaeImeMenuActivated, prefs, callback);
 
   xkb_auto_repeat_enabled_.Init(
       prefs::kLanguageXkbAutoRepeatEnabled, prefs, callback);
@@ -582,6 +588,16 @@ void Preferences::ApplyPreferences(ApplyReason reason,
     ime_state_->SetEnabledExtensionImes(&split_values);
   }
 
+  if (pref_name == prefs::kLangugaeImeMenuActivated &&
+      (reason == REASON_PREF_CHANGED || reason == REASON_ACTIVE_USER_CHANGED)) {
+    const bool activated = ime_menu_activated_.GetValue();
+    if (activated)
+      DVLOG(1) << "IME menu is activated.";
+    else
+      DVLOG(1) << "IME menu is deactivated.";
+    // TODO(azurewei): Fire inputMethodPrivate API event.
+  }
+
   if (user_is_active) {
     system::InputDeviceSettings::Get()->UpdateTouchpadSettings(
         touchpad_settings);