Make the modulemanager.js enhanceable.
Make the modulemanager.js enhanceable.

This is useful for subclasses of modulemanager.js

These subclasses need to be loaded immediately with modulemanager.js, which is exactly the @enhance feature.

RELNOTES: n/a

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=197631100

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