title: Action Bar Back Button is not showing in Android
body: <p>Hi I have created an activity which extends <code>ActionBarActivity</code> &amp; using material theme in my application. In the Action Bar, Back button is not showing. </p>
  
  <p>I didn't find why it is not showing. Any help ?</p>
  
  <pre><code>public class RegistrationActivity extends ActionBarActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_registration);
  
          getSupportActionBar().setBackgroundDrawable(getResources().getDrawable(R.drawable.ab_background_light));
          getSupportActionBar().setDisplayShowHomeEnabled(true);
          getSupportActionBar().setHomeButtonEnabled(true);
          getSupportActionBar().setDisplayHomeAsUpEnabled(true);
  </code></pre>
  
  <p>style.xml</p>
  
  <pre><code>&lt;style name="AppTheme" parent="Theme.AppCompat.Light"&gt;
      &lt;!--Support Library compatibility--&gt;
      &lt;item name="actionBarStyle"&gt;@style/MyTheme.ActionBarStyle&lt;/item&gt;
  &lt;/style&gt;
  
  &lt;!-- ActionBar styles --&gt;
  &lt;style name="MyTheme.ActionBarStyle" parent="@style/Widget.AppCompat.Light.ActionBar"&gt;
      &lt;!--Support Library compatibility--&gt;
      &lt;item name="titleTextStyle"&gt;@style/MyTheme.ActionBar.TitleTextStyle&lt;/item&gt;
  &lt;/style&gt;
  
  &lt;style name="MyTheme.ActionBar.TitleTextStyle" parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Title"&gt;
      &lt;item name="android:textColor"&gt;@android:color/white&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>AndroidManifest.xml</p>
  
  <pre><code>    &lt;activity
          android:name=".RegistrationActivity"
          android:label="@string/title_activity_registration" &gt;
          &lt;meta-data
              android:name="android.support.PARENT_ACTIVITY"
              android:value=".HomeScreenActivity" /&gt;
      &lt;/activity&gt;
  </code></pre>
  
  <p>Thanks in advance.</p>