Minor touch changes for resizing

- Pilfer whenever we cross the threshold in either axis (otherwise
  the app under pip will continue to receive touch events while
  it is resizing)
- Only resize once you pass the threshold, otherwise a sloppy tap
  would trigger an unexpected micro-resize
- Handle cancel when triggering notification from launcher (when
  pip starts pilfering touches and sends a cancel to launcher, it
  should not continue to treat that as an up event and trigger
  notifications to show)

Change-Id: Id31d12484f7ecd55a8e48073979c1886764a9648
Bug: 158887398
Test: Resize PIP, try resizing over home with a swipe down