add 'dart:core' to whitelisted imports
add 'dart:core' to whitelisted imports

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MOE_MIGRATED_REVID=148151681

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