gecko/mobile/android/base/resources/layout/tabs_counter.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- This Source Code Form is subject to the terms of the Mozilla Public
   - License, v. 2.0. If a copy of the MPL was not distributed with this
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<TextView xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:textSize="@dimen/tabs_counter_size"
          android:textColor="@color/tabs_counter_color"
          android:gravity="center"
          android:shadowColor="#7F000000"
          android:shadowRadius="1"
          android:shadowDx="0"
          android:shadowDy="1"/>