Don't disable downward inference inside initializers used for top-level inference.

pkg/analyzer/lib/src/task/dart.dart

 // Copyright (c) 2015, 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 analyzer.src.task.dart;
 
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/standard_resolution_map.dart';
@@ skipping 3746 matching lines @@
       Expression initializer = declaration.initializer;
 
       DartType newType;
       if (!isValidForTypeInference(initializer)) {
         newType = typeProvider.dynamicType;
       } else {
         ResolutionContext resolutionContext =
             ResolutionContextBuilder.contextFor(initializer);
         ResolverVisitor visitor = new ResolverVisitor(
             variable.library, variable.source, typeProvider, errorListener,
-            nameScope: resolutionContext.scope, isTopLevelInference: true);
+            nameScope: resolutionContext.scope);
         if (resolutionContext.enclosingClassDeclaration != null) {
           visitor.prepareToResolveMembersInClass(
               resolutionContext.enclosingClassDeclaration);
         }
         visitor.initForIncrementalResolution();
         initializer.accept(visitor);
         newType = initializer.staticType;
         if (newType == null || newType.isBottom || newType.isDartCoreNull) {
           newType = typeProvider.dynamicType;
         }
@@ skipping 2809 matching lines @@
 
   @override
   bool moveNext() {
     if (_newSources.isEmpty) {
       return false;
     }
     currentTarget = _newSources.removeLast();
     return true;
   }
 }