Fix bug #17900580 Top bar drop shadow no longer transparent

- use the correct padding value depending on the device type: some
padding for large tablet UI when we are in two pane mode. No padding
for all the other cases.

Change-Id: I4863e5c6d2487696334068bd0fe9a91d0fb86cac

core/res/res/values-sw720dp/dimens_material.xml

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (C) 2014 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>
+
+    <!-- Preference activity, vertical padding for the header list -->
+    <dimen name="preference_screen_header_vertical_padding_material">8dp</dimen>
+
+</resources>

core/res/res/values/dimens_material.xml

@@ -15,7 +15,7 @@
 -->
 <resources>
     <!-- Preference activity, vertical padding for the header list -->
-    <dimen name="preference_screen_header_vertical_padding_material">8dp</dimen>
+    <dimen name="preference_screen_header_vertical_padding_material">0dp</dimen>
 
     <!-- Preference activity side margins -->
     <dimen name="preference_screen_side_margin_material">0dp</dimen>