Using single argument for callback and string for projection

This makes the asynchronous and synchronous versions of
readFeatures work with the same data structures, and leaves
projection handling outside the parsers.

src/ol/parser/gpx.js

@@ -12,7 +12,6 @@ goog.require('ol.parser.ObjectFeatureParser');
 goog.require('ol.parser.ReadFeaturesOptions');
 goog.require('ol.parser.StringFeatureParser');
 goog.require('ol.parser.XML');
-goog.require('ol.proj');
 
 
 
@@ -47,7 +46,6 @@ ol.parser.GPX = function(opt_options) {
       'gpx': function(node, obj) {
         if (!goog.isDef(obj.features)) {
           obj.features = [];
-          obj.metadata = {projection: ol.proj.get('EPSG:4326')};
         }
         this.readChildNodes(node, obj);
       },
@@ -245,7 +243,8 @@ ol.parser.GPX.prototype.read = function(data) {
   if (data && data.nodeType == 9) {
     data = data.documentElement;
   }
-  var obj = {features: [], metadata: {projection: ol.proj.get('EPSG:4326')}};
+  var obj = /** @type {ol.parser.ReadFeaturesResult} */
+      ({metadata: {projection: 'EPSG:4326'}});
   this.readNode(data, obj);
   return obj;
 };