Support static field access in analyzer2dart.

pkg/analyzer2dart/lib/src/closed_world.dart

 // Copyright (c) 2014, 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 analyzer2dart.closedWorld;
 
 import 'dart:collection';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 15 matching lines @@
   Map<ExecutableElement, Declaration> executableElements =
       new HashMap<ExecutableElement, Declaration>();
 
   /**
    * Fields that are reachable.
    */
   Map<FieldElement, VariableDeclaration> fields =
       new HashMap<FieldElement, VariableDeclaration>();
 
   /**
+   * Top-level variables that are reachable.
+   */
+  // TODO(johnniwinther): Is there value in splitting fields and top-level
+  // variables?
+  Map<TopLevelVariableElement, VariableDeclaration> variables =
+      new HashMap<TopLevelVariableElement, VariableDeclaration>();
+
+  /**
    * Classes that are instantiated from reachable code.
    *
    * TODO(paulberry): Also keep track of classes that are reachable but not
    * instantiated (because they are extended or mixed in)
    */
   Map<ClassElement, ClassDeclaration> instantiatedClasses =
       new HashMap<ClassElement, ClassDeclaration>();
 
   ClosedWorld(this.mainFunction);
 }