Handle missing maki icons in GeoJson load

[mramato]

Instead of failing the entire load when a maki icon is bad or missing, just create a pin with the icon color instead.

Replaces #2889

Longer term, we probably want a good strategy for missing/bad images throughout the code base. Maybe we have the same "bad image" image that we end up using everywhere?

[hpinkos]

@mramato This change looks good to me. I think we should use the same strategy throughout the Entity API at least. Does KML use icons?

And if you do something like this where the url or the maki name is invalid, it'd be nice to have the pins show up anyway.

var url = Cesium.buildModuleUrl('Assets/Textures/maki/grocery.badpath');
var groceryPin = Cesium.when(pinBuilder.fromUrl(url, Cesium.Color.GREEN, 48), function(canvas) {
    return viewer.entities.add({
        name : 'Grocery store',
        position : Cesium.Cartesian3.fromDegrees(-75.1705217, 39.921786),
        billboard : {
            image : canvas.toDataURL(),
            verticalOrigin : Cesium.VerticalOrigin.BOTTOM
        }
    });
});

//Create a red pin representing a hospital from the maki icon set.
var hospitalPin = Cesium.when(pinBuilder.fromMakiIconId('invalid-name', Cesium.Color.RED, 48), function(canvas) {
    return viewer.entities.add({
        name : 'Hospital',
        position : Cesium.Cartesian3.fromDegrees(-75.1698606, 39.9211275),
        billboard : {
            image : canvas.toDataURL(),
            verticalOrigin : Cesium.VerticalOrigin.BOTTOM
        }
    });
});

If you don't want to tackle this now, could you write up an issue so we can address this and make it consistent everywhere?

[mramato]

And if you do something like this where the url or the maki name is invalid, the when.all never resolves

It's not supposed to resolve, it rejects. This is the desired/expected behavior (of course all of our examples should properly handle rejected promises, which they currently don't. I'll write up an issue for that instead.

The default image stuff has far reaching implications, throughout both the entity and primitive layers, so we definitely shouldn't try and tackle that now.

[hpinkos]

It's not supposed to resolve, it rejects.

Yeah yeah, just realized that a second before you replied. haha

Looks great to me! 👍 Thanks

[pjcozzi]

Should CHANGES.md be updated in master?