src/vs/platform/undoRedo/common/undoRedoService.ts/UndoRedoService/setElementsValidFlag
class UndoRedoService:	public setElementsValidFlag(resource: URI, isValid: boolean, filter: (element: IUndoRedoElement) => boolean): void {
		const strResource = this.getUriComparisonKey(resource);
		if (this._editStacks.has(strResource)) {
			const editStack = this._editStacks.get(strResource)!;
			editStack.setElementsValidFlag(isValid, filter);
		}
		if (DEBUG) {
			this._print('setElementsValidFlag');
		}
	}