Check that interface constructors and default class constructors are compatible.

compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java

Index: compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java b/compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java
index 52ce51356f68ccf168725a92344a033a2b8c124b..2233b8f8aabadbe743047a0d213c5026d79177ab 100644
--- a/compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java
+++ b/compiler/java/com/google/dart/compiler/resolver/ConstructorElement.java
@@ -1,14 +1,22 @@
 // Copyright (c) 2011, 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.
-
 package com.google.dart.compiler.resolver;
 
 public interface ConstructorElement extends MethodElement {
   /**
-   * Returns the type of the instances created by this constructor. Note
-   * that a constructor in a class may be a default implementation of
-   * an interface's constructor.
+   * Returns the type of the instances created by this constructor. Note that a constructor in a
+   * class may be a default implementation of an interface's constructor.
    */
   ClassElement getConstructorType();
+
+  /**
+   * @return the {@link ConstructorElement} in default factory class, may be <code>null</code>.
+   */
+  ConstructorElement getDefaultConstructor();
+
+  /**
+   * Sets {@link ConstructorElement} in default factory class, may be <code>null</code>.
+   */
+  void setDefaultConstructor(ConstructorElement defaultConstructor);
 }