Sharing _delayedMeasurementFinished variable among all instances of moon.Header to avoid unnecessary async measurements for dynamically created headers.
Sharing _delayedMeasurementFinished variable among all instances
of moon.Header to avoid unnecessary async measurements for
dynamically created headers.

Enyo-DCO-1.1-Signed-Off-By: Gray Norton (gray.norton@lge.com)

mcanthony/moonstone,enyojs/moonstone,mcanthony/moonstone,mcanthony/moonstone