Porting over keyboard changes from other branch.

- Allow ignoring alt-key release when interacting via touch while 
  alt-tab is pressed (ag/814903)
- Cancel window animations only if the stack scrolls via alt-tab 
  (ag/809873)
- Fixing issue with old task load plan being consumed if user alt-tabs
  before Recents is resumed (ag/811354)
- Canceling enter animations when the stack scrolls (ag/814461)

Change-Id: I7450f0a280571e98212f321b1e61219d149fed65