chrome/android/java/res/drawable/toolbar_shadow.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2015 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. -->

<transition xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <bitmap
            android:src="@drawable/toolbar_shadow_normal"
            android:gravity="top|fill_horizontal" />
    </item>
    <item>
        <bitmap
            android:src="@drawable/toolbar_shadow_focused"
            android:gravity="top|fill_horizontal" />
    </item>
</transition>