enterFrame(frameId) {
        if (this.contexts) {
            this.lastId++;
            this.contexts = this.contexts.slice();
            this.contexts.push(this.newFrame(this.lastId, frameId));
            this._currentContextIds.unshift(this.contextIdforContexts(this.contexts));
        }
    }
Enter a new frame, a new context is pushed on the current context list.
@param frameId new frame id