Begin hooking up Fasta to analyzer parser tests.

pkg/front_end/lib/src/fasta/builder/scope.dart

 // Copyright (c) 2016, 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.
 
 library fasta.scope;
 
 import 'builder.dart' show
     Builder,
     MixedAccessor;
 
 import '../errors.dart' show
     internalError;
 
 class Scope {
+  /// Names declared in this scope.
   final Map<String, Builder> local;
 
+  /// The scope that this scope is nested within, or `null` if this is the top
+  /// level scope.
   final Scope parent;
 
+  /// Indicates whether an attempt to declare new names in this scope should
+  /// succeed.
   final bool isModifiable;
 
   Scope(this.local, this.parent, {this.isModifiable: true});
 
   Scope createNestedScope({bool isModifiable: true}) {
     return new Scope(<String, Builder>{}, this, isModifiable: isModifiable);
   }
 
   Builder lookup(String name) {
     Builder builder = local[name];
@@ skipping 92 matching lines @@
 
 class AmbiguousBuilder extends Builder {
   final Builder builder;
 
   AmbiguousBuilder(this.builder);
 
   get target => null;
 
   bool get hasProblem => true;
 }