Your bug report

#15294: 24.3.50; js2-mode parser is several times slower in lexical-binding mode

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 15294@debbugs.gnu.org.

-- 
15294: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15294
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