Show selection handles at the correct position for view transformation

The selection handles are implemented based on PopupWindow hence it is
necessary to calculate the transformed location from the TextView's
local coordinates.

This CL only addresses the selection handle locations. Many
functionalities (e.g. selection handle moving direction, handle angle)
doesn't work on transformed view since many components are calculated
on the TextView's local coordinates.

Bug: 24902578
Change-Id: Iaa5fd2812969d097e3bf3219a818ffbc67aaef54