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
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=55127225
First CL on the Compiler fuzzer.

Code for creating random JS expressions.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=55145354
Create a command-line option for the tracer.

Also deleted the method setTracer in CompilerOptions; it was doing the same thing as setTracerMode.
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Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=55151186