Ensure that a string is flattened when entering JsonParser::ParseJson.  Fixes issue v8:1572.
Ensure that a string is flattened when entering JsonParser::ParseJson.  Fixes issue v8:1572.

BUG=v8:1572
TEST=mjsunit/regress/regress-crbug-l84186.js

Review URL: http://codereview.chromium.org/7480044

git-svn-id: b158db1e4b4ab85d4c9e510fdef4b1e8c614b15b@8746 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh