packages/SystemUI/res/values/styles_tv.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
/**
 * Copyright (c) 2016, 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.
 */
-->

<resources xmlns:android="http://schemas.android.com/apk/res/android">
    <style name="PipTheme" parent="@android:style/Theme.Translucent.NoTitleBar.Fullscreen">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:backgroundDimEnabled">false</item>
     </style>

    <style name="RecentsTvTheme.Wallpaper" parent="@android:style/Theme.Material.NoActionBar.Overscan">
        <item name="android:windowBackground">@android:color/transparent</item>
        <item name="android:backgroundDimEnabled">false</item>
        <item name="android:colorBackgroundCacheHint">@null</item>
        <item name="android:windowIsTranslucent">true</item>
    </style>
</resources>