Update the mutationobserver type signature. The constructor callback function takes two parameters:

1. The array of mutation records.
2. The observer that triggered the callback.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=64808715
Closure Compiler collections cleanups
- get rid of unchecked warnings in various places
- prefer ImmutableList to Arrays.asList
- use EnumMap/ImmutableMap in Keywords
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=64809592
Add a way to hook in computation before/after all passes
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=64810377