Fix handling of default formal parameters in DeclarationResolver.

pkg/analyzer/test/src/context/context_test.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 analyzer.test.src.context.context_test;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 2457 matching lines @@
 
 class ClassTwo {
   // Implicit no-argument constructor
 }
 
 void topLevelFunctionWithLocalFunction() {
   void localFunction({bool b: false}) {}
 }
 
 void functionWithGenericFunctionTypedParam/*<S>*/(/*=T*/ pf/*<T>*/(/*=T*/ e)) {}
+void functionWithClosureAsDefaultParam([x = () => null]) {}
 ''');
     context.resolveCompilationUnit2(source, source);
     LibraryElement firstElement = context.computeLibraryElement(source);
     _ElementGatherer gatherer = new _ElementGatherer();
     firstElement.accept(gatherer);
 
     CacheEntry entry =
         context.analysisCache.get(new LibrarySpecificUnit(source, source));
     entry.setState(RESOLVED_UNIT1, CacheState.FLUSHED);
     entry.setState(RESOLVED_UNIT2, CacheState.FLUSHED);
@@ skipping 2800 matching lines @@
    * Initialize the visitor.
    */
   _ElementGatherer();
 
   @override
   void visitElement(Element element) {
     elements[element] = element;
     super.visitElement(element);
   }
 }