Add check for undefined references in default parameters.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=71154393
Hoist variables declared in a generator to the enclosing closure so that their state is maintained between calls to the generator.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=71186330