session-android/res/drawable/conversation_item_sent_push_triangle_shape.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
    <item>
        <rotate android:fromDegrees="45"
                android:toDegrees="45"
                android:pivotX="0%"
                android:pivotY="-30%">
            <shape android:shape="rectangle">
                <solid android:color="@color/conversation_item_sent_push_background_light" />
            </shape>
        </rotate>
    </item>
</layer-list>