Add polyfill for Object.assign()

src/ol/object.js

@@ -1,12 +1,42 @@
 goog.provide('ol.Object');
 goog.provide('ol.ObjectEvent');
 goog.provide('ol.ObjectEventType');
+goog.provide('ol.object');
 
 goog.require('ol.events');
 goog.require('ol.events.Event');
 goog.require('ol.Observable');
 
 
+/**
+ * Polyfill for Object.assign().  Assigns enumerable and own properties from
+ * one or more source objects to a target object.
+ *
+ * @see https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
+ * @param {!Object} target The target object.
+ * @param {...Object} var_sources The source object(s).
+ * @return {!Object} The modified target object.
+ */
+ol.object.assign = (typeof Object.assign === 'function') ? Object.assign : function(target, var_sources) {
+  if (target === undefined || target === null) {
+    throw new TypeError('Cannot convert undefined or null to object');
+  }
+
+  var output = Object(target);
+  for (var i = 1, ii = arguments.length; i < ii; ++i) {
+    var source = arguments[i];
+    if (source !== undefined && source !== null) {
+      for (var key in source) {
+        if (source.hasOwnProperty(key)) {
+          output[key] = source[key];
+        }
+      }
+    }
+  }
+  return output;
+};
+
+
 /**
  * @enum {string}
  */