Implement Reference.refersTo() in UnstartedRuntime.

Complement the Reference.get() implementation with the
Reference.refersTo(). This may prevent initialization
regressions for some classes as we replace Reference.get()
uses with Reference.refersTo() in the future.

Test: m
Bug: 172573708
Change-Id: I03b6ba9b06f8da0f38761f21c21ef15e7517c47d
2 files changed