Remove support for interface in dart2js.

sdk/lib/_internal/compiler/implementation/tools/mini_parser.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 parser;
 
 import 'dart:io';
 import 'dart:typed_data';
 import 'dart:collection';
 import 'dart:utf';
@@ skipping 211 matching lines @@
 
   void endClassDeclaration(int interfacesCount, Token beginToken,
                            Token extendsKeyword, Token implementsKeyword,
                            Token endToken) {
     super.endClassDeclaration(interfacesCount, beginToken,
                               extendsKeyword, implementsKeyword,
                               endToken);
     ClassNode node = popNode(); // Discard ClassNode and assert the type.
   }
 
-  void endInterface(int supertypeCount, Token interfaceKeyword,
-                    Token extendsKeyword, Token endToken) {
-    super.endInterface(supertypeCount, interfaceKeyword, extendsKeyword,
-                       endToken);
-    ClassNode node = popNode(); // Discard ClassNode and assert the type.
-  }
-
   void endTopLevelFields(int count, Token beginToken, Token endToken) {
     super.endTopLevelFields(count, beginToken, endToken);
     VariableDefinitions node = popNode(); // Discard node and assert the type.
   }
 
   void endFunctionTypeAlias(Token typedefKeyword, Token endToken) {
     super.endFunctionTypeAlias(typedefKeyword, endToken);
     Typedef node = popNode(); // Discard Typedef and assert type type.
   }
 
@@ skipping 63 matching lines @@
   set text(String newText) {
     throw "not supported";
   }
 }
 
 class Mock {
   const Mock();
   bool get useColors => true;
   internalError(message) { throw message.toString(); }
 }