Account for OHM offset during PIP drag corner resize

The InputEventReceiver in PipResizeGestureHandler receives
global coordinates in its events (i.e. screen coordinates)
that need to be translated into the PIP's window position.

Bug: 172839150
Test: enter PIP, enter OHM, drag resize
Change-Id: If5aaa8940904046ffc2303574e272601589a1638