title: Display Back Arrow on Toolbar
body: <p>I'm migrating from <code>ActionBar</code> to <code>Toolbar</code> in my application. 
  But I don't know how to display and set click event on Back Arrow on <code>Toolbar</code> like I did on <code>Actionbar</code>.  </p>
  
  <p><img src="https://i.stack.imgur.com/avYnD.png" alt="enter image description here"></p>
  
  <p>With <code>ActionBar</code>, I call <code>mActionbar.setDisplayHomeAsUpEnabled(true)</code>.
  But there is no the similar method like this.</p>
  
  <p>Has anyone ever faced this situation and somehow found a way to solve it?</p>