src/vs/workbench/common/views.ts/ViewsRegistry/deregisterViews
class ViewsRegistry:	deregisterViews(viewDescriptors: IViewDescriptor[], viewContainer: ViewContainer): void {
		const views = this.removeViews(viewDescriptors, viewContainer);
		if (views.length) {
			this._onViewsDeregistered.fire({ views, viewContainer });
		}
	}