src/vs/platform/undoRedo/common/undoRedoService.ts/ResourceEditStack/setElementsValidFlag
class ResourceEditStack:	public setElementsValidFlag(isValid: boolean, filter: (element: IUndoRedoElement) => boolean): void {
		for (const element of this._past) {
			if (filter(element.actual)) {
				this._setElementValidFlag(element, isValid);
			}
		}
		for (const element of this._future) {
			if (filter(element.actual)) {
				this._setElementValidFlag(element, isValid);
			}
		}
	}