src/vs/platform/undoRedo/common/undoRedoService.ts/ResourceEditStack/_setElementValidFlag
class ResourceEditStack:	private _setElementValidFlag(element: StackElement, isValid: boolean): void {
		if (element.type === UndoRedoElementType.Workspace) {
			element.setValid(this.resourceLabel, this.strResource, isValid);
		} else {
			element.setValid(isValid);
		}
	}