packages/SystemUI/res/layout/bubble_expanded_view.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
  ~ Copyright (C) 2018 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.bubbles.BubbleExpandedView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:id="@+id/bubble_expanded_view">

    <View
        android:id="@+id/pointer_view"
        android:layout_width="@dimen/bubble_pointer_width"
        android:layout_height="@dimen/bubble_pointer_height"
    />

    <com.android.systemui.statusbar.AlphaOptimizedButton
        style="@android:style/Widget.Material.Button.Borderless"
        android:id="@+id/settings_button"
        android:layout_gravity="start"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:focusable="true"
        android:text="@string/manage_bubbles_text"
        android:textColor="?attr/wallpaperTextColor"
    />

</com.android.systemui.bubbles.BubbleExpandedView>