Automated g4 rollback of changelist 54802220.

*** Reason for rollback ***

breakages

*** Original change description ***

Check for unnecessary casts in the TypeCheck pass.

***
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=54829791
Externs file for the latest version of underscore (1.5.2).
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=54891014
Add on, off, and triggerHandler methods to angular.JQLite typedef.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=54911107
Fix wrong declaration in w3c_audio.js.

AudioContext.prototype.createChannelSplitter and AudioContext.prototype.createChannelMerger can both take an optional number parameter.

https://dvcs.w3.org/hg/audio/raw-file/tip/webaudio/specification.html#AudioContext-section
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=54916382