title: How to replace title by logo in Android Toolbar?
body: <p>I want to replace the title in my Toolbar by a logo like <a href="https://lh3.ggpht.com/Fd9sjOix7dWiiaVtx-3lF9o96m0ST0px39sV6CsySxuuXobB_wrMBaBZApp1S9L6d0IH=h900-rw" rel="nofollow">Twitter App</a>.</p>
  
  <p>I think we can replace this programmatically like that :</p>
  
  <pre><code>mToolbar = (Toolbar) findViewById(R.id.app_toolbar);
  mToolbar.setLogo(R.drawable.ic_logo);
  </code></pre>
  
  <p>But I want to replace it directly in my XML toolBar declaration, but I can't see the property <code>app:logo</code> or <code>android:logo</code>.</p>
  
  <pre><code>&lt;android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto"
      android:id="@+id/app_toolbar"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:background="@color/colorPrimary"
      android:minHeight="?attr/actionBarSize"
      app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
      app:theme="@style/MyCustomToolBarTheme" /&gt;
  </code></pre>
  
  <p>Please help me, thank you.</p>