Use URL instead of Url or url in comments and strings

src/ol/source/tilewmssource.js

@@ -147,7 +147,7 @@ ol.source.TileWMS.prototype.getFeatureInfoForPixel =
       offset = map.getPixelFromCoordinate(ol.extent.getTopLeft(tileExtent)),
       url = this.tileUrlFunction(tileCoord, projection);
   goog.asserts.assert(goog.isDef(url),
-      'ol.source.TileWMS#tileUrlFunction does not return a url');
+      'ol.source.TileWMS#tileUrlFunction does not return a URL');
   ol.source.wms.getFeatureInfo(url,
       [pixel[0] - offset[0], pixel[1] - offset[1]], this.getFeatureInfoOptions_,
       success, opt_error);