feat(olcs): Use OL tile load functions rather than Cesium's

This is related to (and based on) openlayers/ol-cesium#562 and openlayers/ol-cesium#37. However, we

need it for GeoPackage support rather than for reprojection. Additionally, this helps support any

other custom tile classes and tile load functions in Cesium.

Author: wallw-dev

externs/Cesium.externs.js

@@ -75,6 +75,13 @@ Cesium.Deferred = function() {};
  */
 Cesium.Deferred.prototype.resolve = function(value) {};
 
+/**
+ * Rejector for a deferred.
+ * @param {*=} opt_value
+ * @template T
+ */
+Cesium.Deferred.prototype.reject = function(opt_value) {};
+
 
 /**
  * @type {Cesium.Promise}

src/os/mapcontainer.js

@@ -69,7 +69,6 @@ goog.require('os.ogc');
 goog.require('os.ol.control.MousePosition');
 goog.require('os.ol.feature');
 goog.require('os.olcs.Camera');
-goog.require('os.olcs.WMSImageryProvider');
 goog.require('os.olcs.sync.RootSynchronizer');
 goog.require('os.proj');
 goog.require('os.proj.switch');
@@ -1601,7 +1600,6 @@ os.MapContainer.prototype.initCesium_ = function() {
       os.olcs.loadCesium().then(function() {
         try {
           os.mixin.cesium.loadCesiumMixins();
-          os.olcs.WMSImageryProvider.init();
           this.registerTerrainProviderType('cesium', Cesium.CesiumTerrainProvider);
 
           this.olCesium_ = new olcs.OLCesium({

src/os/mixin/urltilemixin.js

@@ -10,11 +10,13 @@ goog.require('ol.source.TileEventType');
 goog.require('ol.source.UrlTile');
 goog.require('os.events.PropertyChangeEvent');
 goog.require('os.implements');
+goog.require('os.ol.source.ILoadingSource');
 goog.require('os.ol.source.IUrlSource');
 
 
 // add support for providing custom URL parameters
 os.implements(ol.source.UrlTile, os.ol.source.IUrlSource.ID);
+os.implements(ol.source.UrlTile, os.ol.source.ILoadingSource.ID);
 
 
 /*

src/os/ol/source/iloadingsource.js

@@ -7,6 +7,11 @@ goog.provide('os.ol.source.ILoadingSource');
  */
 os.ol.source.ILoadingSource = function() {};
 
+/**
+ * @type {string}
+ * @const
+ */
+os.ol.source.ILoadingSource.ID = 'os.ol.source.ILoadingSource';
 
 /**
  * If the source is currently in a loading state.