chrome/android/java/res/menu/website_preferences_menu.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. -->

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/search"
          android:title="@string/search"
          app:showAsAction="always"
          app:actionViewClass="android.support.v7.widget.SearchView" />
</menu>