Remove uses of "head" Rhino
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68057120
Adding externs for Promise#all and Promise#race.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68106410
Extended logic for array literals containing spreads to support function calls containing spreads as arguments.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68126631
Add the ability to parse and print array comprehensions.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=68131489