Remove a bad heuristic when determining click location for accessibility.

As a bride-gap solution to click on partially covered views in accessibility
mode we compute a point on the screen where to send a down/up event pair.
A heuristic we used was that if the action target is covered by a view that
that has a touch listener we consider the target obscured by the one with
the listener. However, this generates false positives, for example the target
is covered by a view that observers touches for scrolling but not clicking.

bug:18782023

Change-Id: I31ff34011d45667f1eddda47373ec00e4a23dbf6