gecko-dev/mobile/android/base/resources/layout/tabs_panel_view.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
   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->

<org.mozilla.gecko.tabspanel.TabsPanel xmlns:android="http://schemas.android.com/apk/res/android"
                                       android:id="@+id/tabs_panel"
                                       android:layout_width="match_parent"
                                       android:layout_height="match_parent"
                                       android:background="@color/background_tabs"/>