Allow watch rotary to trigger stretch on scrolling containers.

Bug: 204794759

Rotary scrolling should trigger the stretch edge effect. Mouse
scrolling should NOT trigger the stretch edge effect. This
adds support for rotary scrolling while keeping mouse scrolling
from triggering the edge effect.

Test: new CTS tests. manual testing on emulator
Change-Id: Ibad25bcbc0740f2af2042baf67f7606f15b8c57e