Fix RegionSamplingHelper race condition

mSamplingRequestBounds was causing a race condition in RegionSamplingHelper because it becomes an empty Rectangle in the main thread when the background thread needs it to be non-empty for CompositionSamplingListener.register().To fix this, a final copy of mSamplingRequestBounds is passed to the background thread, so that it will always be working with a non-empty Rectangle.

Test: atest testCompositionSamplingListener_has_nonEmptyRect
Fixes: 247690841
Change-Id: Ib0139c8be80f828172e1909503dcf57a59673717