title: Background (rounded corners) of a recycler view does not appear without adding some padding
body: <p>I have the following drawable:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;  
  &lt;shape xmlns:android="http://schemas.android.com/apk/res/android"&gt;  
      &lt;solid android:color="@android:color/white"/&gt;  
      &lt;corners android:radius="6dp"/&gt;  
  &lt;/shape&gt;   
  </code></pre>
  
  <p>Adding that to a recyclerview using <code>android:background="@drawable/my_bg_drawable"</code> does not seem to work.<br>
  I included a LinearLayout to wrap the recycler view and added the background to the LinearLayout but that had no effect either.<br>
  The following worked:  </p>
  
  <pre><code>&lt;LinearLayout android:layout_width="match_parent"  
         android:layout_height="wrap_content"  
         android:layout_marginLeft="10dp"  
         android:layout_marginRight="10dp"  
         android:padding="2dp"  
         android:background="@drawable/my_bg_drawable"&gt;    
              &lt;android.support.v7.widget.RecyclerView  
                          android:layout_width="match_parent"  
                          android:layout_height="wrap_content"  
                      /&gt;  
  
         &lt;/LinearLayout&gt;  
  </code></pre>
  
  <p>Basically adding the padding <code>android:padding="2dp"</code> allowed the background to become visible (at least that was when the corners showed up).<br>
  Why does this work like this and I have to use padding?</p>