Add and extend widget tests to check KEYCODE_ESCAPE clears popups

With the change in ag/15212330, KEYCODE_ESCAPE should now also close
popups that can be closed with KEYCODE_BACK.  Extend existing tests
and add a new testcase in ListPopupWindowTest to check this is true.

Bug: 174164194
Test: Run modified test sets on a board with and without the patch from
    ag/15212330
Change-Id: I82bc2e3f67dce6f17a83a9bd4f9e1145288c3bec
3 files changed