refactor: make extractPropertyNames behaviour a bit more obvious.
refactor: make extractPropertyNames behaviour a bit more obvious.

hterkelsen/ts2dart,jeffbcross/ts2dart,hansl/ts2dart,hterkelsen/ts2dart,jacob314/ts2dart,jacob314/ts2dart,hansl/ts2dart,dart-archive/ts2dart,dart-archive/ts2dart,jeffbcross/ts2dart,dart-archive/ts2dart