packages/SystemUI/res/layout/status_bar_notification_section_header.xml

<!--
  ~ Copyright (C) 2019 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
  -->

<!-- Extends FrameLayout -->
<com.android.systemui.statusbar.notification.stack.SectionHeaderView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="@dimen/notification_section_header_height"
    android:paddingStart="4dp"
    android:paddingEnd="4dp"
    android:focusable="true"
    android:clickable="true"
    >

    <LinearLayout
        android:id="@+id/content"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        android:gravity="center_vertical"
        android:orientation="horizontal"
        android:forceHasOverlappingRendering="false"
        android:clipChildren="false"
        >
        <FrameLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:gravity="start|center_vertical"
            android:layout_weight="1">

            <TextView
                style="@style/TextAppearance.NotificationSectionHeaderButton"
                android:id="@+id/header_label"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:forceHasOverlappingRendering="false"
                android:text="@string/notification_section_header_gentle"
            />

        </FrameLayout>
        <ImageView
            android:id="@+id/btn_clear_all"
            android:layout_width="48dp"
            android:layout_height="48dp"
            android:src="@drawable/status_bar_notification_section_header_clear_btn"
            android:contentDescription="@string/accessibility_notification_section_header_gentle_clear_all"
            android:scaleType="center"
            android:tint="?attr/wallpaperTextColor"
            android:tintMode="src_in"
            android:visibility="gone"
            android:forceHasOverlappingRendering="false"
        />
    </LinearLayout>

</com.android.systemui.statusbar.notification.stack.SectionHeaderView>