Remove support for interface in dart2js.

sdk/lib/_internal/compiler/implementation/mirrors/dart2js_mirror.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.
 
 library mirrors_dart2js;
 
 import 'dart:async';
 import 'dart:collection' show LinkedHashMap;
 import 'dart:uri';
 
@@ skipping 807 matching lines @@
     Link<DartType> link = _class.interfaces;
     while (!link.isEmpty) {
       var type = _convertTypeToTypeMirror(mirrors, link.head,
                                           mirrors.compiler.types.dynamicType);
       list.add(type);
       link = link.tail;
     }
     return list;
   }
 
-  bool get isClass => !_class.isInterface();
+  bool get isClass => true;
 
-  bool get isInterface => _class.isInterface();
+  bool get isInterface => false;
 
   bool get isAbstract => _class.modifiers.isAbstract();
 
   bool get isOriginalDeclaration => true;
 
   List<TypeMirror> get typeArguments {
     throw new UnsupportedError(
         'Declarations do not have type arguments');
   }
 
   List<TypeVariableMirror> get typeVariables {
     if (_typeVariables == null) {
       _typeVariables = <TypeVariableMirror>[];
       _class.ensureResolved(mirrors.compiler);
       for (TypeVariableType typeVariable in _class.typeVariables) {
         _typeVariables.add(
             new Dart2JsTypeVariableMirror(mirrors, typeVariable));
       }
     }
     return _typeVariables;
   }
 
   /**
    * Returns the default type for this interface.
    */
   ClassMirror get defaultFactory {
-    if (_class.defaultClass != null) {
-      return new Dart2JsInterfaceTypeMirror(mirrors, _class.defaultClass);
-    }
     return null;
   }
 
   bool operator ==(Object other) {
     if (identical(this, other)) {
       return true;
     }
     if (other is! ClassMirror) {
       return false;
     }
@@ skipping 838 matching lines @@
  *
  * All API in this class is experimental.
  */
 class BackDoor {
   /// Return the compilation units comprising [library].
   static List<Mirror> compilationUnitsOf(Dart2JsLibraryMirror library) {
     return library._element.compilationUnits.toList().map(
         (cu) => new Dart2JsCompilationUnitMirror(cu, library)).toList();
   }
 }