java/com/android/incallui/incall/impl/res/drawable/incall_button_background_more.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
  <item>
    <selector>
      <item
        android:drawable="@drawable/incall_button_background_checked"
        android:state_checked="true"/>
      <item android:drawable="@drawable/incall_button_background_unchecked"/>
    </selector>
  </item>
  <item>
    <ripple android:color="@color/incall_button_ripple">
      <item
        android:id="@android:id/mask"
        android:gravity="center">
        <shape android:shape="oval">
          <solid android:color="@android:color/white"/>
        </shape>
      </item>
    </ripple>
  </item>

  <!-- This adds a little down arrow to indicate that the button will pop up a menu. Use an explicit
    <bitmap> to avoid scaling the icon up to the full size of the button. -->
  <item>
    <bitmap
      android:gravity="end"
      android:src="@drawable/quantum_ic_arrow_drop_down_white_18"/>
  </item>
</layer-list>