Remove frog from the repository.

frog/await/nodeset.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-/** Weak set of AST nodes. */
-// TODO(sigmund): delete this. This is a temporary workaround to keep 'frog'
-// as independent as possible of the await experimental feature. Ideally we
-// should either make [Node] hashable or store information collected by analyses
-// in the nodes themselves.
-class NodeSet {
-  Map<String, List<Node>> _hashset;
-  NodeSet() : _hashset = {};
-
-  bool add(Node n) {
-    if (contains(n)) return false;
-    String key = n.span.locationText;
-    List<Node> nodes = _hashset[key];
-    if (nodes == null) {
-      _hashset[key] = [n];
-    } else {
-      nodes.add(n);
-    }
-    return true;
-  }
-
-  bool contains(Node n) {
-    String key = n.span.locationText;
-    List<Node> nodes = _hashset[key];
-    if (nodes == null) {
-      return false;
-    }
-    for (Node member in nodes) {
-      if (n === member) return true;
-    }
-    return false;
-  }
-}