Migrate trackpad 3-finger swipe to pull down notifications away from ShadeViewController.handleExternalTouch

TODO - still work needs to be done for swiping up from shade to close it

Bug: 331916995
Test: Enable flexiglass, use 3-finger swipe down from home, app, or overview to pull down shade
Change-Id: I21d82d788ab011f497025dd913680783f8363617
1 file changed