AttachedSurfaceControl: Respond to API feedback.

"Root" is eliminated from the interface name as it is a property
of the object and not the interface, but remains highlighted in the
getters to express the relationship between the called and returned
object.

Bug: 185365821
Test: Existing tests pass
Change-Id: I163fc23f2c37c984ef3ffeb7514c4d8c1c1a3f90