Allow customisation of advanced settings in DocumentsUI

Enables the customisation of the default value of the DocumentsUI
'advanced' setting using overlays.

Change-Id: I240cbb845d15ab2ea6ae7a79a17b4f51905fdb9c

packages/DocumentsUI/res/values/config.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2015 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+<resources>
+    <!-- Allow Advanced Devices default value to be customised -->
+    <bool name="config_defaultAdvancedDevices">false</bool>
+</resources>

packages/DocumentsUI/src/com/android/documentsui/LocalPreferences.java

@@ -24,8 +24,10 @@ public class LocalPreferences {
     private static final String KEY_FILE_SIZE = "fileSize";
 
     public static boolean getDisplayAdvancedDevices(Context context) {
+        boolean defaultAdvanced = context.getResources()
+                .getBoolean(R.bool.config_defaultAdvancedDevices);
         return PreferenceManager.getDefaultSharedPreferences(context)
-                .getBoolean(KEY_ADVANCED_DEVICES, false);
+                .getBoolean(KEY_ADVANCED_DEVICES, defaultAdvanced);
     }
 
     public static boolean getDisplayFileSize(Context context) {