Distinct PolylineCollections for each CustomDataSource

CustomDataSources were using the same PolylineCollection to store their Polyline primitives. When a CustomDataSource was destroyed, it was also destroying the PolylineCollection. Since that object was shared and other CustomDataSources remained in the system, this would cause Cesium to stop rendering when the destroyed PolylineCollection was accessed.

Solution: use distinct PolylineCollections per CustomDataSource by keying PolylineCollections with the PrimitiveCollection's guid in addition to the Scene id.

packages/engine/Source/DataSources/PolylineGeometryUpdater.js

@@ -661,12 +661,12 @@ function getLine(dynamicGeometryUpdater) {
     return dynamicGeometryUpdater._line;
   }
 
-  const sceneId = dynamicGeometryUpdater._geometryUpdater._scene.id;
-  let polylineCollection = polylineCollections[sceneId];
   const primitives = dynamicGeometryUpdater._primitives;
+  const polylineCollectionId = dynamicGeometryUpdater._geometryUpdater._scene.id + primitives._guid;
+  let polylineCollection = polylineCollections[polylineCollectionId];
   if (!defined(polylineCollection) || polylineCollection.isDestroyed()) {
     polylineCollection = new PolylineCollection();
-    polylineCollections[sceneId] = polylineCollection;
+    polylineCollections[polylineCollectionId] = polylineCollection;
     primitives.add(polylineCollection);
   } else if (!primitives.contains(polylineCollection)) {
     primitives.add(polylineCollection);
@@ -869,14 +869,14 @@ DynamicGeometryUpdater.prototype.isDestroyed = function () {
 
 DynamicGeometryUpdater.prototype.destroy = function () {
   const geometryUpdater = this._geometryUpdater;
-  const sceneId = geometryUpdater._scene.id;
-  const polylineCollection = polylineCollections[sceneId];
+  const polylineCollectionId = geometryUpdater._scene.id + this._primitives._guid;
+  const polylineCollection = polylineCollections[polylineCollectionId];
   if (defined(polylineCollection)) {
     polylineCollection.remove(this._line);
     if (polylineCollection.length === 0) {
       removePolylineCollection(geometryUpdater._scene.primitives, polylineCollection);
       this._primitives.removeAndDestroy(polylineCollection);
-      delete polylineCollections[sceneId];
+      delete polylineCollections[polylineCollectionId];
     }
   }
   if (defined(this._groundPolylinePrimitive)) {