cherry picking from esprima harmony branch
cherry picking from esprima harmony branch

commit 261b80e97c11cbc1097f425d1ea75e5a2e143491

sweet-js/sweet.js,mozilla/sweet.js,getshuvo/sweet.js,dashersw/sweet.js,mozilla/sweet.js,sweet-js/sweet-core,renyaoxiang/sweet.js,dashersw/sweet.js,sweet-js/sweet.js,renyaoxiang/sweet.js,getshuvo/sweet.js