Support static field access in analyzer2dart.

pkg/analyzer2dart/lib/src/closed_world.dart

Index: pkg/analyzer2dart/lib/src/closed_world.dart
diff --git a/pkg/analyzer2dart/lib/src/closed_world.dart b/pkg/analyzer2dart/lib/src/closed_world.dart
index 4c21271c89336a2f94a388bfc7b82de84f443b98..fbcdaa47eb671c573cec3322cdb34fc7cfb18276 100644
--- a/pkg/analyzer2dart/lib/src/closed_world.dart
+++ b/pkg/analyzer2dart/lib/src/closed_world.dart
@@ -33,6 +33,14 @@ class ClosedWorld {
       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