Implement local storage for App List in case app sync is off.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 0c5edd74b37f22a1a4868c56883f5e0719759ec7..db9d3473e893caf4da651a23afbb0c66385e588f 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -2106,6 +2106,9 @@ const char kAppListEnableMethod[] = "app_list.how_enabled";
 // The time that the app launcher was enabled. Cleared when UMA is recorded.
 const char kAppListEnableTime[] = "app_list.when_enabled";
 
+// Keeps local state of app list while sync service is not available.
+const char kAppListLocalState[] = "app_list.local_state";
+
 #if defined(OS_MACOSX)
 // Integer representing the version of the app launcher shortcut installed on
 // the system. Incremented, e.g., when embedded icons change.