Clone NearFarScalar values in constructor for Billboard, Label and PointPrimitive

[hpinkos]

In master, these two billboards have different behavior when you click the update button because the scaleByDistance setter clones the NearFarScalar but the constructor does not. This updates the constructor so it also clones the value passed in.

var viewer = new Cesium.Viewer('cesiumContainer');
var scene = viewer.scene;

var scalar = new Cesium.NearFarScalar(1.5e2, 2.0, 1.5e7, 0.5);

var billboards1 = scene.primitives.add(new Cesium.BillboardCollection());
var b1 = billboards1.add({
    image : '../images/facility.gif',
    position : Cesium.Cartesian3.fromDegrees(-75, 40),
    scaleByDistance : scalar
});

var billboards2 = scene.primitives.add(new Cesium.BillboardCollection());
var b2 = billboards2.add();
b2.image = '../images/facility.gif';
b2.position = Cesium.Cartesian3.fromDegrees(-76, 40);
b2.scaleByDistance = scalar;

Sandcastle.addToolbarButton('Update', function() {
    scalar.far = 1.5e5;
    b1.scaleByDistance = scalar;
    b2.scaleByDistance = scalar;
});

[mramato]

As a counter argument, should we be cloning at all? Isn't this extremely memory inefficient if you want to share the same values across all billboards?

[hpinkos]

In all of the primitives I just looked at, any time we pass in a Cartesian3 or Matrix4 or other objects we always clone them. Just for consistency alone, I think we should make this change. If we want to revisit 'should we really be cloning' it should be across the board.

[hpinkos]

Thanks @bagnell!

[bagnell]

As a counter argument, should we be cloning at all? Isn't this extremely memory inefficient if you want to share the same values across all billboards?

As far as I know, we clone all options to a constructor/setter. This prevents users from constructing with one object, changing the value and constructing another object.

[pjcozzi]

Sounds like this fixes a bug-ish / changes behavior.

Please update CHANGES.md in master.

[hpinkos]

Done 8bc1760