Allow ES6 Promises to be returned by labs.Environment setUp() and setUpPage()
Allow ES6 Promises to be returned by labs.Environment setUp() and setUpPage()

RELNOTES: same

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=222851113

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