SF: Moving Vsync modulator away from threads.

Modulator should not know about threads, just make a request to scheduler
whenever it's ready to update the offsets.

Bug: 113612090
Test: SF tests pass. Ran systrace -- offsetting works as expected.
Change-Id: Iaff11208ab8d1aa8a7c35a28e6802c1ca04e5243
2 files changed