Fix an edge case in computing click location in accessibility mode.

In accessibility mode to click a view we computed a point where to send
down and up touch events. The logic that computes where to send the
events was not clipping the bounds of the child to these of the parent.
As a result we wrongly computed we can send the events in a location
of the child that is outside of its parent, thus the click having no
effect or clicking the wrong thing.

bug:18672945

Change-Id: If9c452e7e5b196f699db33d37dbc6775d5d1622a