chromium/chrome/browser/feed/android/java/res/drawable/header_title_tab_selected_background.xml

<?xml version="1.0" encoding="utf-8"?>
<!--
Copyright 2023 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

<selector xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
  <item android:state_selected="false" >
    <shape android:shape="rectangle">
      <!-- This will show the main background color. -->
      <solid android:color="@android:color/transparent"/>
    </shape>
  </item>
  <item android:state_selected="true" >
    <shape android:shape="rectangle">
      <!-- The stroke will show the main background color. -->
      <stroke android:width="8dp" android:color="@android:color/transparent"/>
      <solid android:color="@color/color_primary_with_alpha_15"/>
      <corners android:radius="@dimen/feed_header_background_corner_radius"/>
    </shape>
  </item>
</selector>