src/vs/workbench/contrib/notebook/browser/notebookRendererMessagingServiceImpl.ts/NotebookRendererMessagingService/prepare
class NotebookRendererMessagingService:	public prepare(rendererId: string) {
		if (this.activations.has(rendererId)) {
			return;
		}

		const queue: MessageToSend[] = [];
		this.activations.set(rendererId, queue);

		this.extensionService.activateByEvent(`onRenderer:${rendererId}`).then(() => {
			for (const message of queue) {
				this.postMessageEmitter.fire(message);
			}

			this.activations.set(rendererId, undefined);
		});
	}