Text handles positions' are correctly updated.

Bug 3510106

The CAB animation does not fire events, which does not update the
handles' positions.

The solution is to make the handle update their position before any
draw traversal, using an onPreDrawListener. The ScrollingPopupWindow
onScroll listener is no longer needed with this change. This is also
a more robust solution since other events (such as animations) may
change the TextView's position.

The cost is a recomputation of the Handles' positions at each redraw
which was not necessary with listeners. But as mentioned before, not
all possible events provide listeners or will in the future.

Change-Id: I0f46118de5f660a75d95eecb2cf987fcb4b3b322