Remove support for interface in dart2js.

sdk/lib/_internal/compiler/implementation/scanner/keyword.dart

 // 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.
 
 part of scanner;
 
 /**
  * A keyword in the Dart programming language.
  */
 class Keyword extends IterableBase<int> implements SourceString {
@@ skipping 36 matching lines @@
 
       const Keyword("abstract", isBuiltIn: true),
       const Keyword("as", info: AS_INFO, isBuiltIn: true),
       const Keyword("dynamic", isBuiltIn: true),
       const Keyword("export", isBuiltIn: true),
       const Keyword("external", isBuiltIn: true),
       const Keyword("factory", isBuiltIn: true),
       const Keyword("get", isBuiltIn: true),
       const Keyword("implements", isBuiltIn: true),
       const Keyword("import", isBuiltIn: true),
-      const Keyword("interface", isBuiltIn: true),
       const Keyword("library", isBuiltIn: true),
       const Keyword("operator", isBuiltIn: true),
       const Keyword("part", isBuiltIn: true),
       const Keyword("set", isBuiltIn: true),
       const Keyword("static", isBuiltIn: true),
       const Keyword("typedef", isBuiltIn: true),
 
       const Keyword("hide", isPseudo: true),
       const Keyword("native", isPseudo: true),
       const Keyword("of", isPseudo: true),
@@ skipping 155 matching lines @@
  */
 class LeafKeywordState extends KeywordState {
   LeafKeywordState(String syntax) : super(Keyword.keywords[syntax]);
 
   bool isLeaf() => true;
 
   KeywordState next(int c) => null;
 
   String toString() => keyword.syntax;
 }