packages/SystemUI/res/layout/controls_onboarding.xml

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

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
    android:padding="4dp"
    android:orientation="vertical">

    <View
        android:id="@+id/arrow"
        android:elevation="2dp"
        android:layout_width="10dp"
        android:layout_height="8dp"
        android:layout_marginBottom="-2dp"
        android:layout_gravity="center_horizontal"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingStart="24dp"
        android:paddingEnd="4dp"
        android:background="@drawable/recents_onboarding_toast_rounded_background"
        android:layout_gravity="center_horizontal"
        android:elevation="2dp"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/onboarding_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:layout_gravity="center_vertical"
            android:textColor="?attr/wallpaperTextColor"
            android:textSize="16sp"/>
        <ImageView
            android:id="@+id/dismiss"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:layout_gravity="center_vertical"
            android:padding="10dp"
            android:layout_marginStart="2dp"
            android:layout_marginEnd="2dp"
            android:alpha="0.7"
            android:src="@drawable/ic_close_white"
            android:tint="?attr/wallpaperTextColor"
            android:background="?android:attr/selectableItemBackgroundBorderless"
            android:contentDescription="@string/accessibility_desc_close"/>
    </LinearLayout>
</LinearLayout>