(bug 49264) Handle bad values using UnDeserializableValue.

This introduces the UnDeserializableValue. object which can optionally
be used to represent bad (uninterpretable) values in a larger data structure.

Change-Id: I9920286723e04ba2005b608583c45338f53d21fd
Merge "(bug 49264) Handle bad values using UnDeserializableValue."