src/vs/editor/common/model/pieceTreeTextBuffer/pieceTreeBase.ts/PieceTreeSnapshot/constructor
class PieceTreeSnapshot:	constructor(tree: PieceTreeBase, BOM: string) {
		this._pieces = [];
		this._tree = tree;
		this._BOM = BOM;
		this._index = 0;
		if (tree.root !== SENTINEL) {
			tree.iterate(tree.root, node => {
				if (node !== SENTINEL) {
					this._pieces.push(node.piece);
				}
				return true;
			});
		}
	}