[Boundary interfaces] Add utility methods for support library boundary am: 7b527a9a1c am: 5177c1d7ef
am: b127c8d137

Change-Id: I2156a1fcddd7cc3676f58d599b6d6a2b236ea8a5
tree: 1c764c01c6c0bee2e5937f81a9706c19343a4e2d
  1. src/
  2. BUILD.gn
  3. DEPS