If a string passed to eval starts with '[', it's reasonable to try the JSON parser. We did this for '(' in bug 578216.
We should work out the test failures in bug 578216 first, though!
Created attachment 578897 [details] [diff] [review]
This takes about 1/3 of the time and should be safe to do.
Comment on attachment 578897 [details] [diff] [review]