Simplify goog.function.TRUE/FALSE/NULL definition.
Simplify goog.function.TRUE/FALSE/NULL definition.

This will help compiler to remove more dead code.

RELNOTES: n/a

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=214991083

lucidsoftware/closure-library,lucidsoftware/closure-library,teppeis/closure-library,teppeis/closure-library,lucidsoftware/closure-library,lucidsoftware/closure-library,teppeis/closure-library,google/closure-library,google/closure-library,google/closure-library,google/closure-library,teppeis/closure-library,google/closure-library