ol.source.WMTS now passes tileClass option to ol.source.TileImage

The constructor for ol.source.TileImage accepts an option for the tileClass,
but ol.source.WMTS does not pass this to the parent. This pull request adds
that in.

externs/olx.js

@@ -3599,7 +3599,7 @@ olx.source.TileImageOptions.prototype.state;
 
 
 /**
- * tile class
+ * Class used to instantiate image tiles. Default is {@link ol.ImageTile}.
  * @type {function(new: ol.ImageTile, ol.TileCoord,
  *                 ol.TileState, string, ?string,
  *                 ol.TileLoadFunctionType)|undefined}
@@ -4996,7 +4996,10 @@ olx.source.StaticVectorOptions.prototype.urls;
  *     url: (string|undefined),
  *     maxZoom: (number|undefined),
  *     tileLoadFunction: (ol.TileLoadFunctionType|undefined),
- *     urls: (Array.<string>|undefined)}}
+ *     urls: (Array.<string>|undefined),
+ *     tileClass: (function(new: ol.ImageTile, ol.TileCoord,
+ *                          ol.TileState, string, ?string,
+ *                          ol.TileLoadFunctionType)|undefined)}}
  * @api
  */
 olx.source.WMTSOptions;
@@ -5066,6 +5069,16 @@ olx.source.WMTSOptions.prototype.layer;
 olx.source.WMTSOptions.prototype.style;
 
 
+/**
+ * Class used to instantiate image tiles. Default is {@link ol.ImageTile}.
+ * @type {function(new: ol.ImageTile, ol.TileCoord,
+ *                 ol.TileState, string, ?string,
+ *                 ol.TileLoadFunctionType)|undefined}
+ * @api
+ */
+olx.source.WMTSOptions.prototype.tileClass;
+
+
 /**
  * The pixel ratio used by the tile service. For example, if the tile
  * service advertizes 256px by 256px tiles but actually sends 512px

src/ol/source/wmtssource.js

@@ -181,6 +181,7 @@ ol.source.WMTS = function(options) {
     crossOrigin: options.crossOrigin,
     logo: options.logo,
     projection: options.projection,
+    tileClass: options.tileClass,
     tileGrid: tileGrid,
     tileLoadFunction: options.tileLoadFunction,
     tilePixelRatio: options.tilePixelRatio,