src/vs/workbench/common/views.ts/ViewsRegistry/registerViewWelcomeContent
class ViewsRegistry:	registerViewWelcomeContent(id: string, viewContent: IViewContentDescriptor): IDisposable {
		this._viewWelcomeContents.add(id, viewContent);
		this._onDidChangeViewWelcomeContent.fire(id);

		return toDisposable(() => {
			this._viewWelcomeContents.delete(id, viewContent);
			this._onDidChangeViewWelcomeContent.fire(id);
		});
	}