Fix a regression where android:windowContentOverlay did not draw properly.

This was the victim of an earlier refactoring. Have the
ActionBarOverlayLayout draw this directly over the content so that it
can stay properly in sync with any animations and also remove an extra
couple of views from the decor layout.

Some apps now expect the broken behavior in default themes. Protect
them from themselves until they bump their targetSdkVersion.

Public bug https://code.google.com/p/android/issues/detail?id=58280

Change-Id: I4284503577e322f3e68d4a7fabda8441d3749b98