function ContainerLoop() {
    this._updates = [];
    this._stoppedAt = now();
    this._sleep = 0;

    this.start();

    var _this = this;
    window.addEventListener('message', function(ev) {
        _this._onWindowMessage(ev);
    });
}
Loop class used for updating objects on a frame-by-frame. Synchronizes the
`update` method invocations to the refresh rate of the screen.
Does not normalize the high resolution timestamp when being consecutively
started and stopped.

@class ContainerLoop