Add @const annotation for Char.
Add @const annotation for Char.

This forces use of implicit type instead of defaulting to *.

RELNOTES: jsaction.Char constant is now marked @const

	Change on 2018/10/02 by urmillab <urmillab@google.com>

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=215450138

google/jsaction,google/jsaction