dandelion/app/src/main/res/layout/main__content.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/content_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context=".activity.MainActivity"
    tools:showIn="@layout/main__app_bar">

    <FrameLayout
        android:id="@+id/placeholder_webview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_alignParentEnd="true"
        android:layout_alignParentStart="true"
        android:layout_centerVertical="true"/>

    <ProgressBar
        android:id="@+id/progressBar"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        style="@style/Widget.AppCompat.ProgressBar.Horizontal"
        android:layout_width="fill_parent"
        android:indeterminate="false"
        android:layout_height="wrap_content"
        android:layout_marginTop="-7dp" />

</RelativeLayout>