Because android.support.v7.app.ActionBarActivity
alters the window content by adding an ActionBar.
Please take a look at the code starting with
@Override
protected void onCreate(Bundle savedInstanceState) {
mImpl = ActionBarActivityDelegate.createDelegate(this);
super.onCreate(savedInstanceState);
mImpl.onCreate(savedInstanceState);
}
and on at https://android.googlesource.com/platform/frameworks/support/+/master/v7/appcompat/src/android/support/v7/app/ActionBarActivity.java for details.
And what the FEATURE_INDETERMINATE_PROGRESS
looks like depends on whether an ActionBar is present or not. So that needs to be set before the super call.