title: colorControlHighlight doesn't change color of flat button when pressed
body: <p>I need to change color of materials flat/borderless button when the user clicks on it. My current setup works for raised buttons, but doesn't work for the borderless button. </p>
  
  <p>Style I use, the <code>colorControlHighlight</code> should change the color when pressed?:</p>
  
  <pre><code>&lt;style name="PrimaryFlatButton" parent="Widget.AppCompat.Button.Borderless.Colored"&gt;
  &lt;item name="colorButtonNormal"&gt;@color/primary_color&lt;/item&gt;
  &lt;item name="colorControlHighlight"&gt;@color/primary_color_dark&lt;/item&gt;
  &lt;item name="colorAccent"&gt;@color/primary_color&lt;/item&gt;
  &lt;item name="android:textColor"&gt;@color/white_color&lt;/item&gt;
  </code></pre>
  
  <p></p>
  
  <p>Layout item:</p>
  
  <pre><code>  &lt;Button
      android:id="@+id/Btn_SignUp"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:theme="@style/PrimaryFlatButton" /&gt;
  </code></pre>
  
  <p>Why does raised buttons work but not borderless?</p>