Use json.encode/json.decode. This gets some strings wrong but it
should be enough to make more progress.
Testing with hardcoded strings is already getting awkward.
Change-Id: Ie0b168bec611ed93da13fff90f86232bb56c713f
Reviewed-on: https://dart-review.googlesource.com/c/87663
Reviewed-by: Daniel Hillerström <hillerstrom@google.com>
Commit-Queue: Kevin Millikin <kmillikin@google.com>