chrome/android/java/res/drawable/thumbnail_gradient_top_left.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">

    <!-- The spec for the gradient is #25272B applied at 6% transparency. This gives #0F25272B. -->

    <gradient
        android:angle="315"
        android:startColor="#0F25272B"
        android:endColor="#00000000" />
</shape>