Fix runtime type error
Fix runtime type error

We're currently suppressing cast failures around list.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=157007459

angulardart/angular,kevmoo/angular,matanlurey/angular,kevmoo/angular,angulardart/angular,chalin/angular2,chalin/angular2,matanlurey/angular,matanlurey/angular,angulardart/angular,kevmoo/angular,chalin/angular2