Using a dedicated object for value storage

Without this, we are limited in the key names that we can accept from users.  And because of compiler renaming, we don't know ahead of time what the limitations are (e.g. the key 'a' may clobber the 'set' method).

src/ol/object.js

@@ -39,6 +39,13 @@ ol.ObjectProperty = {
  */
 ol.Object = function(opt_values) {
   goog.base(this);
+
+  /**
+   * @private
+   * @type {Object.<string, *>}
+   */
+  this.values_ = {};
+
   if (goog.isDef(opt_values)) {
     this.setValues(opt_values);
   }
@@ -164,6 +171,7 @@ ol.Object.prototype.changed = goog.nullFunction;
  * @return {*} Value.
  */
 ol.Object.prototype.get = function(key) {
+  var value;
   var accessors = ol.Object.getAccessors(this);
   if (accessors.hasOwnProperty(key)) {
     var accessor = accessors[key];
@@ -171,13 +179,14 @@ ol.Object.prototype.get = function(key) {
     var targetKey = accessor.key;
     var getterName = ol.Object.getGetterName(targetKey);
     if (target[getterName]) {
-      return target[getterName]();
+      value = target[getterName]();
     } else {
-      return target.get(targetKey);
+      value = target.get(targetKey);
     }
-  } else {
-    return this[key];
+  } else if (this.values_.hasOwnProperty(key)) {
+    value = this.values_[key];
   }
+  return value;
 };
 
 
@@ -225,7 +234,7 @@ ol.Object.prototype.set = function(key, value) {
       target.set(targetKey, value);
     }
   } else {
-    this[key] = value;
+    this.values_[key] = value;
     this.notifyInternal_(key);
   }
 };
@@ -266,7 +275,7 @@ ol.Object.prototype.unbind = function(key) {
     var value = this.get(key);
     var accessors = ol.Object.getAccessors(this);
     delete accessors[key];
-    this[key] = value;
+    this.values_[key] = value;
   }
 };