public createSnapshot(resource: URI): ResourceEditStackSnapshot {
for (let i = 0, len = this._past.length; i < len; i++) {
elements.push(this._past[i].id);
}
for (let i = this._future.length - 1; i >= 0; i--) {
elements.push(this._future[i].id);
}
return new ResourceEditStackSnapshot(resource, elements);
}
public restoreSnapshot(snapshot: ResourceEditStackSnapshot): void {