Don't allow new of interface without constructors.

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

Index: compiler/java/com/google/dart/compiler/resolver/Elements.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/Elements.java b/compiler/java/com/google/dart/compiler/resolver/Elements.java
index f9a37350ce250fca438fc8153af8486ae255b760..e47c7ee9994710bf180fe5863f7c30d5cf82ea3e 100644
--- a/compiler/java/com/google/dart/compiler/resolver/Elements.java
+++ b/compiler/java/com/google/dart/compiler/resolver/Elements.java
@@ -239,7 +239,8 @@ public class Elements {
    * Returns true if the class needs an implicit default constructor.
    */
   public static boolean needsImplicitDefaultConstructor(ClassElement classElement) {
-    return !classElement.isObject() && classElement.getConstructors().isEmpty();
+    return !classElement.isObject() && classElement.getConstructors().isEmpty()
+        && (!classElement.isInterface() || classElement.getDefaultClass() != null);
   }
 
   /**