title: Plus Icon in Floating Action Button not rendered correctly in Android pre-Lollipop
body: <p>I tried to setup a fab by using the support design library.</p>
  
  <p>Code in XML:</p>
  
  <pre><code>&lt;android.support.design.widget.FloatingActionButton
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:id="@+id/fab"
      android:src="@drawable/ic_add_white_18dp"
      app:borderWidth="2dp"
      app:fabSize="normal"
      android:onClick="submit"
      app:rippleColor="@color/colorPrimaryDark"&gt;
  
  &lt;/android.support.design.widget.FloatingActionButton&gt;
  </code></pre>
  
  <p>On Nexus 6(lollipop), the plus icon is rendering correctly.</p>
  
  <p><img src="https://i.stack.imgur.com/oHvPX.png" alt="enter image description here"></p>
  
  <p>But on nexus 4(pre lollipop), plus icon size is crossing the circle.</p>
  
  <p><img src="https://i.stack.imgur.com/nVlBn.png" alt="enter image description here"></p>
  
  <p>I have downloaded and used the plus(ic_add_white_18dp) from <a href="https://www.google.com/design/icons/index.html" rel="nofollow noreferrer">Material icons</a></p>
  
  <p>Icon Sizes used:</p>
  
  <pre><code>mdpi - 18dp
  hdpi - 27dp
  xdpi - 36dp
  xxdpi - 54dp
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/Bdd15.png" alt="enter image description here"></p>
  
  <p><strong>What should be the correct size to use for plus icon.</strong></p>