As part of this CL, object reference tracking is implemented (and tested with a
self-referential object). This sort of reference tracking will be shared with
other receivers (array, date, regexp and host objects).

Not included in this CL is compatibility with version-0 objects (which don't
support a non-tree object graph, and require a little stack to correctly
deserialize).

BUG=chromium:148757

Review-Url: https://codereview.chromium.org/2246093003
Cr-Commit-Position: refs/heads/master@{#38683}