lawnchair/quickstep/res/drawable/gesture_tutorial_action_button_background.xml

<!--
    Copyright (C) 2020 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

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    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item>
        <shape
            android:id="@android:id/mask"
            android:shape="rectangle">
            <corners android:radius="50dp"/>
        </shape>
    </item>
    <item>
        <shape
            android:shape="rectangle">
            <corners android:radius="50dp"/>
            <solid android:color="@color/gesture_tutorial_primary_color"/>
        </shape>
    </item>
</layer-list>