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GroundPolylinePrimitive._initializeTerrainHeightsWorker fails when app is served via a proxied domain

See original GitHub issue

GroundPolylinePrimitive._initializeTerrainHeightsWorker tries to load in the approximateTerrainHeights.json from a relative path.

GroundPolylinePrimitive.js

ApproximateTerrainHeights.initialize('../Assets/approximateTerrainHeights.json')

This then calls the buildModuleUrl function with that path before passing it to Resource.fetchJson

ApproximateTerrainHeights.js

ApproximateTerrainHeights._initPromise = Resource.fetchJson(buildModuleUrl(url)).then(function(json) {
            ApproximateTerrainHeights._terrainHeights = json;
        });

buildModuleUrl first does a check to see if it’s running in node by checking typeof document === 'undefined' and if true, it just returns moduleID.

When inside a web worker, document is undefined and the relative path is returned as it would be in node. This is fine when the code is being accessed on the same domain as it’s being served on.

But when you proxy the app, the relative path becomes http://proxied-url.com/../Assets/approximateTerrainHeights.json which doesn’t exist as the JSON is being served on a different domain and so the Resource.fetchJson blows up.