Update app widget resize frame UI.

Mock: https://docs.google.com/presentation/d/1UxdDh8EFhPbdRWRwzjbpgL-j02ew4Ew3eG3XBCeoYdo/edit#slide=id.8YyBaHq
Implementation: https://screenshot.googleplex.com/BEFwWBmXXx8xXdS

I will update the drag handles in a follow-up CL since their specs
aren't ready yet.

Test: manual
Bug: 181774580
Change-Id: I19a99e6dbe106754da0fac56a5c2e7eb9eb90cef