[Android] Update AppMenu to use the same background as stock Android menu.

chrome/android/java/res/layout/four_button_menu_item.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2014 The Chromium Authors. All rights reserved.
 
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file.
 -->
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:layout_gravity="top|start"
     android:orientation="horizontal">
 
     <ImageButton
         android:id="@+id/button_one"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_weight="1"
-        android:background="?android:attr/selectableItemBackground"
+        android:background="?android:attr/listChoiceBackgroundIndicator"
         android:scaleType="center" />
 
     <View
         android:layout_width="1dp"
         android:layout_height="?android:attr/listPreferredItemHeightSmall"
         android:background="?android:attr/listDivider" />
 
     <ImageButton
         android:id="@+id/button_two"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_weight="1"
-        android:background="?android:attr/selectableItemBackground"
+        android:background="?android:attr/listChoiceBackgroundIndicator"
         android:scaleType="center" />
 
     <View
         android:layout_width="1dp"
         android:layout_height="?android:attr/listPreferredItemHeightSmall"
         android:background="?android:attr/listDivider" />
 
     <ImageButton
         android:id="@+id/button_three"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_weight="1"
-        android:background="?android:attr/selectableItemBackground"
+        android:background="?android:attr/listChoiceBackgroundIndicator"
         android:scaleType="center" />
     
     <View
         android:layout_width="1dp"
         android:layout_height="?android:attr/listPreferredItemHeightSmall"
         android:background="?android:attr/listDivider" />
 
     <ImageButton
         android:id="@+id/button_four"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
         android:layout_weight="1"
-        android:background="?android:attr/selectableItemBackground"
+        android:background="?android:attr/listChoiceBackgroundIndicator"
         android:scaleType="center" />
 
 </LinearLayout>