CompositeProperty throws if TimeInterval's data is not a Property

[thw0rted]

Sandcastle example

Browser: Chrome

Operating System: Win10

I started with the Sandcastle demo for Interpolation, thinking it would be an easy way to see how CompositeProperty works. (Incidentally, there is no current Sandcastle demo that uses this class.) It's throwing and the error message doesn't make it obvious why.

Try to pause around property.intervals.addInterval(interval); with the debugger and step through until you get to CompositeProperty#subscribeAll. eventHelper.add throws when interval.data.definitionChanged is undefined.

One of two things needs to happen: if data is an arbitrary value with no definitionChanged event, skip the subscribe step; OR, update the docs for CompositeProperty (or I guess TimeInterval? probably not?) to specify that data must be a Property.

[thw0rted]

To clarify, simply wrapping the data in new Cesium.ConstantPositionProperty(...) makes it work as I expected. I just wanted to help any future users that can't understand why passing arbitrary data isn't working.