packages/SystemUI/res/layout/navigation_bar.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
**
** Copyright 2011, 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.
*/
-->

<com.android.systemui.statusbar.phone.NavigationBarView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:systemui="http://schemas.android.com/apk/res-auto"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:background="@drawable/system_bar_background">

    <com.android.systemui.CornerHandleView
        android:id="@+id/assist_hint_left"
        android:layout_width="36dp"
        android:layout_height="36dp"
        android:layout_gravity="left|bottom"
        android:rotation="270"
        android:visibility="gone"/>
    <com.android.systemui.CornerHandleView
        android:id="@+id/assist_hint_right"
        android:layout_width="36dp"
        android:layout_height="36dp"
        android:layout_gravity="right|bottom"
        android:rotation="180"
        android:visibility="gone"/>

    <com.android.systemui.statusbar.phone.NavigationBarInflaterView
        android:id="@+id/navigation_inflater"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</com.android.systemui.statusbar.phone.NavigationBarView>