chrome/android/java/res/drawable/btn_back.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.
-->

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_enabled="false" android:drawable="@drawable/btn_back_disabled" />
    <item android:state_pressed="true" android:drawable="@drawable/btn_back_pressed" />
    <item android:state_selected="true" android:drawable="@drawable/btn_back_pressed" />
    <item android:state_focused="true" android:drawable="@drawable/btn_back_pressed" />
    <item android:drawable="@drawable/btn_back_normal" />
</selector>