packages/SystemUI/res/layout/status_bar_notification_section_header_contents.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
  -->

<!-- Used by both status_bar_notification_header and SectionHeaderView -->
<merge xmlns:android="http://schemas.android.com/apk/res/android" >
    <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"
    />
</merge>