I guess you could combine it like this:
<?xml version="1.0" encoding="UTF-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:left="6dp"
android:right="6dp">
<shape android:shape="rectangle">
<gradient android:startColor="#ccd0d3"
android:centerColor="#b6babd"
android:endColor="#ccd0d3"
android:height="1px"
android:angle="0"/>
</shape>
</item>
</layer-list>