core/res/res/layout/notification_template_header.xml

<?xml version="1.0" encoding="utf-8"?><!--
  ~ Copyright (C) 2015 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 -->
<NotificationHeaderView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/notification_header"
    android:layout_width="match_parent"
    android:layout_height="@dimen/notification_header_height"
    android:layout_marginBottom="@dimen/notification_header_margin_bottom"
    android:clipChildren="false"
    android:gravity="center_vertical"
    android:orientation="horizontal"
    android:theme="@style/Theme.DeviceDefault.Notification"
    android:importantForAccessibility="no"
    >

    <ImageView
        android:id="@+id/left_icon"
        android:layout_width="@dimen/notification_left_icon_size"
        android:layout_height="@dimen/notification_left_icon_size"
        android:layout_alignParentStart="true"
        android:layout_centerVertical="true"
        android:layout_marginStart="@dimen/notification_left_icon_start"
        android:background="@drawable/notification_large_icon_outline"
        android:clipToOutline="true"
        android:importantForAccessibility="no"
        android:scaleType="centerCrop"
        android:visibility="gone"
        />

    <com.android.internal.widget.CachingIconView
        android:id="@+id/icon"
        android:layout_width="@dimen/notification_icon_circle_size"
        android:layout_height="@dimen/notification_icon_circle_size"
        android:layout_alignParentStart="true"
        android:layout_centerVertical="true"
        android:layout_marginStart="@dimen/notification_icon_circle_start"
        android:background="@drawable/notification_icon_circle"
        android:padding="@dimen/notification_icon_circle_padding"
        android:maxDrawableWidth="@dimen/notification_icon_circle_size"
        android:maxDrawableHeight="@dimen/notification_icon_circle_size"
        />

    <!-- extends ViewGroup -->
    <NotificationTopLineView
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/notification_top_line"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_alignParentStart="true"
        android:layout_centerVertical="true"
        android:layout_toStartOf="@id/expand_button"
        android:layout_alignWithParentIfMissing="true"
        android:clipChildren="false"
        android:gravity="center_vertical"
        android:paddingStart="@dimen/notification_content_margin_start"
        android:theme="@style/Theme.DeviceDefault.Notification"
        >

        <include layout="@layout/notification_top_line_views" />

    </NotificationTopLineView>

    <FrameLayout
        android:id="@+id/alternate_expand_target"
        android:layout_width="@dimen/notification_content_margin_start"
        android:layout_height="match_parent"
        android:layout_alignParentStart="true"
        android:importantForAccessibility="no"
        />

    <include layout="@layout/notification_expand_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentEnd="true"
        android:layout_centerVertical="true"
        />

</NotificationHeaderView>