通知領域のキャリア名非表示
status_bar_expanded.xml
<TextView android:textAppearance="@style/TextAppearance.StatusBar.Expanded.Network.EmergencyOnly"～
<TextView android:textAppearance="@style/TextAppearance.StatusBar.Expanded.Network"～
それぞれの後ろに
android:textSize="0.0sp" android:maxLength="0"
を追加

通知の「全て削除」ボタンの角丸化
status_bar_expanded_header.xml
<Button android:id="@id/clear_all_button"～の後に
android:background="@drawable/button_design"
を追加

resdrawableにbutton_design.xmlを追加

<?xml version="1.0" encoding="utf-8"?>
<selector
    xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true">
        <shape
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:shape="rectangle">
            <corners
                android:radius="15dp" />
        </shape>
        <color android:color="#7f000000" />
    </item>
    <item android:state_pressed="false">
        <shape
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:shape="rectangle">
            <corners
                android:radius="15dp" />
        </shape>
        <color android:color="#7f000000" />
    </item>
</selector>