ListPopupWindow should use window layout type SUB_PANEL

Look down, back up, where are you? You're in a dialog with an
AutoCompleteTextView. What's on your screen? I have it, it's the
auto-completion results you could be seeing. Look again. The window
layout type is now TYPE_APPLICATION_SUB_PANEL and the auto-completion
results are visible.

Also adds API on ListPopupWindow to specify the window layout type
and changes the text editing handle to be type ABOVE_SUB_PANEL.

Bug: 18530738
Change-Id: Id5577c4892729920de5b73411e580e6b2b2401d0