Use a list instead of identical hashset, for cycle-detection in JSON stringify.
Use a list instead of identical hashset, for cycle-detection in JSON stringify.

Currently, identicalHashCodes are somewhat expensive on the VM, due to
runtime-calls.

BUG=
R=lrn@google.com

Review URL: https://codereview.chromium.org//209473003

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@34299 260f80e4-7a28-3924-810f-c04153c831b5

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