code: function (mergeTo, mergeFrom, classpathTo) {
          var hasEvents = false;
          for (var k in mergeFrom) {
              if (mergeFrom.hasOwnProperty(k)) {
                  if (!hasEvents) {
                      hasEvents = true;
                  }
                  // The comparison with null below is important, as an empty string is a valid event description.
                  if (mergeTo[k] != null) {
                      Aria.$logError(Aria.REDECLARED_EVENT, [k, classpathTo]);
                  } else {
                      mergeTo[k] = mergeFrom[k];
                  }
              }
          }
          return hasEvents;
      }
docs: Copies the content of mergeFrom into mergeTo. mergeFrom and mergeTo are maps of event definitions. If an event
  declared in mergeFrom already exists in mergeTo, the error is logged and the event is not overriden.
  @name Aria.__mergeEvents
  @private
  @method
  @param {Object} mergeTo Destrination object (map of events).
  @param {Object} mergeFrom Source object (map of events).
  @param {String} Classpath of the object to which events are copied. Used in case of error.
  @return {Boolean} false if mergeFrom is empty. True otherwise.