Accessibility: Ignore overlapping siblings when computing a click location

To click a view we were computing a click location by ignoring overlapping
views that are actionable. However, detection whether a view is actionable
is not always possible as the view may handle touch events directly. This
leads to unhandled edge cases. We are taking a conservative approach and
ignore all overlapping siblings regardless if clickable. This is also has
limitations but hopefully less frequent edge cases.

bug:18889611

Change-Id: Icea0b7b3e2d4ed53e50e01cb6a99b880be560b14