Refactoring getPreferenceKey method

This method was returnning a constant and getting inlined by proguard.

Change-Id: I87348e25b21483adc1b27d16f99dec4b73205701
diff --git a/src/com/android/launcher3/Utilities.java b/src/com/android/launcher3/Utilities.java
index 2ed9a25..d14d056 100644
--- a/src/com/android/launcher3/Utilities.java
+++ b/src/com/android/launcher3/Utilities.java
@@ -137,7 +137,7 @@
 
     public static boolean isAllowRotationPrefEnabled(Context context, boolean multiProcess) {
         SharedPreferences sharedPrefs = context.getSharedPreferences(
-                LauncherAppState.getSharedPreferencesKey(), Context.MODE_PRIVATE | (multiProcess ?
+                LauncherFiles.SHARED_PREFERENCES_KEY, Context.MODE_PRIVATE | (multiProcess ?
                         Context.MODE_MULTI_PROCESS : 0));
         boolean allowRotationPref = sharedPrefs.getBoolean(ALLOW_ROTATION_PREFERENCE_KEY, false);
         return sForceEnableRotation || allowRotationPref;
@@ -754,4 +754,9 @@
     public static int longCompare(long lhs, long rhs) {
         return lhs < rhs ? -1 : (lhs == rhs ? 0 : 1);
     }
+
+    public static SharedPreferences getPrefs(Context context) {
+        return context.getSharedPreferences(
+                LauncherFiles.SHARED_PREFERENCES_KEY, Context.MODE_PRIVATE);
+    }
 }