Expand Keys enum to include all whitespace keys and all navigation keys: added tab, space, page down, page up.
Expand Keys enum to include all whitespace keys and all navigation keys: added tab, space, page down, page up.

Key values reference: https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values

RELNOTES: KeyboardEvent.key now includes tab, space, page down, and page up keys.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=212465339

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