title: ShareActivityProvider does not show up as a button
body: <p>My ShareActionProvider does not show an icon.  My app crashes if I showAsAction. It does provide a share action, I just want it to show a button with an icon instead of the word, and I want to set showAsAction to "always." My inflate code is here:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;android.support.design.widget.CoordinatorLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  xmlns:app="http://schemas.android.com/apk/res-auto"                                    
  android:id="@+id/main_content"
  android:layout_width="match_parent" android:layout_height="match_parent"
  android:fitsSystemWindows="true" tools:context=".MainActivity"
  style="@style/AppTheme"&gt;
  
  &lt;android.support.design.widget.AppBarLayout android:id="@+id/appbar"
      android:layout_width="match_parent" android:layout_height="wrap_content"
      android:paddingTop="@dimen/appbar_padding_top"
      android:theme="@style/AppTheme.AppBarOverlay"&gt;
  
      &lt;android.support.v7.widget.Toolbar android:id="@+id/toolbar"
          android:layout_width="match_parent" android:layout_height="? 
   attr/actionBarSize"
          android:background="?attr/colorPrimary"   
  app:popupTheme="@style/AppTheme.PopupOverlay"
          app:layout_scrollFlags="scroll|enterAlways"&gt;
          &lt;android.support.design.widget.TabLayout
              android:id="@+id/tabs"
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              app:tabMode="fixed"
              app:tabGravity="fill" /&gt;
  
      &lt;/android.support.v7.widget.Toolbar&gt;
  
  &lt;/android.support.design.widget.AppBarLayout&gt;
  
  &lt;android.support.v4.view.ViewPager android:id="@+id/container"
      android:layout_width="match_parent" android:layout_height="match_parent"
      app:layout_behavior="@string/appbar_scrolling_view_behavior" /&gt;
  
  
  &lt;/android.support.design.widget.CoordinatorLayout&gt;
  </code></pre>
  
  <p>For the menu, my XML is here.  I'm using the v7 compatibility library.</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  
  &lt;menu xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools" tools:context=".MainActivity"&gt;
  &lt;item android:id="@+id/action_settings"    
  android:title="@string/action_settings"
      android:orderInCategory="100" app:showAsAction="never"
      /&gt;
  &lt;item
      android:id="@+id/menu_item_share"
      android:title="Share"
      app:actionProviderClass="support.v7.android.widget.ShareActionProvider"
      app:showAsAction="never"/&gt;
  &lt;/menu&gt;
  </code></pre>