title: Elevation shadow not visible for Toolbar with Basic Activity
body: <p>I created a "Basic Activity" with Android Studio and attempted to create an elevation shadow on an API 28 Pixel device, using the answer from <a href="https://stackoverflow.com/questions/56818304/toolbar-not-showing-elevation-in-android-9-api-28?noredirect=1&amp;lq=1">toolbar-not-showing-elevation-in-android-9-api-28</a>. However, there is no elevation shadow displayed. The <code>activity_main.xml</code> file currently is:</p>
  
  <pre><code>&lt;androidx.coordinatorlayout.widget.CoordinatorLayout
          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:layout_width="match_parent"
          android:layout_height="match_parent"
          tools:context=".MainActivity"&gt;
  
      &lt;com.google.android.material.appbar.AppBarLayout
              android:layout_height="wrap_content"
              android:layout_width="match_parent"
              app:elevation="0dp"
              android:theme="@style/AppTheme.AppBarOverlay"&gt;
  
          &lt;androidx.appcompat.widget.Toolbar
                  android:id="@+id/toolbar"
                  android:layout_width="match_parent"
                  android:elevation="16dp"
                  android:layout_height="?attr/actionBarSize"
                  android:background="?attr/colorPrimary"
                  app:popupTheme="@style/AppTheme.PopupOverlay"/&gt;
  
      &lt;/com.google.android.material.appbar.AppBarLayout&gt;
  
      &lt;include layout="@layout/content_main"/&gt;
  
      &lt;com.google.android.material.floatingactionbutton.FloatingActionButton
              android:id="@+id/fab"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_gravity="bottom|end"
              android:layout_margin="@dimen/fab_margin"
              app:srcCompat="@android:drawable/ic_dialog_email"/&gt;
  
  &lt;/androidx.coordinatorlayout.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>Why does the elevation shadow no longer work on <code>Toolbar</code>?</p>