src/vs/workbench/contrib/bulkEdit/browser/bulkEditService.ts/BulkEditService/setPreviewHandler
class BulkEditService:	setPreviewHandler(handler: IBulkEditPreviewHandler): IDisposable {
		this._previewHandler = handler;
		return toDisposable(() => {
			if (this._previewHandler === handler) {
				this._previewHandler = undefined;
			}
		});
	}