Expose default constructors through ClassElement.localMembers.

dart/sdk/lib/_internal/compiler/implementation/dart_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 400 matching lines @@
           const Link<DartType>()
           );
       constructor.cachedNode = new FunctionExpression(
           new Send(classNode.name, synthesizedIdentifier),
           new NodeList(new StringToken(OPEN_PAREN_INFO, '(', -1),
                        const Link<Node>(),
                        new StringToken(CLOSE_PAREN_INFO, ')', -1)),
           new EmptyStatement(new StringToken(SEMICOLON_INFO, ';', -1)),
           null, Modifiers.EMPTY, null, null);
 
-      classMembers[classElement].add(constructor);
+      if (!constructor.isSynthesized) {
+        classMembers[classElement].add(constructor);
+      }
       elementAsts[constructor] =
           new ElementAst(constructor.cachedNode, new TreeElementMapping(null));
     }
 
     // Create all necessary placeholders.
     PlaceholderCollector collector =
         new PlaceholderCollector(compiler, fixedMemberNames, elementAsts);
     // Add synthesizedIdentifier to set of unresolved names to rename it to
     // some unused identifier.
     collector.unresolvedNodes.add(synthesizedIdentifier);
@@ skipping 156 matching lines @@
 }
 
 compareElements(e0, e1) {
   int result = compareBy((e) => e.getLibrary().canonicalUri.toString())(e0, e1);
   if (result != 0) return result;
   return compareBy((e) => e.position().charOffset)(e0, e1);
 }
 
 List<Element> sortElements(Iterable<Element> elements) =>
     sorted(elements, compareElements);