Bug 867064 - Fix homescreen panning test due r=crdlc a=npotb

Move from mouse events to touch events.
Send both event types so that we won't fail in some situations.

also mock requestAnimationFrame in the suiteSetup instead of setup.
(cherry picked from commit f317b4afa829448177bdac9a00248eff10cf572e)

Conflicts:
	apps/homescreen/test/unit/grid_test.js