Remove support for interface in dart2js.

sdk/lib/_internal/compiler/implementation/resolution/scope.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.
 
 part of resolution;
 
 abstract class Scope {
   /**
    * Adds [element] to this scope. This operation is only allowed on mutable
    * scopes such as [MethodScope] and [BlockScope].
@@ skipping 27 matching lines @@
   static Scope buildEnclosingScope(Element element) {
     return element.enclosingElement != null
         ? element.enclosingElement.buildScope() : element.buildScope();
   }
 }
 
 /**
  * [TypeDeclarationScope] defines the outer scope of a type declaration in
  * which the declared type variables and the entities in the enclosing scope are
  * available but where declared and inherited members are not available. This
- * scope is only used for class/interface declarations during resolution of the
+ * scope is only used for class declarations during resolution of the
  * class hierarchy. In all other cases [ClassScope] is used.
  */
 class TypeDeclarationScope extends NestedScope {
   final TypeDeclarationElement element;
 
   TypeDeclarationScope(parent, this.element)
       : super(parent) {
     assert(parent != null);
   }
 
@@ skipping 95 matching lines @@
 
   Element localLookup(SourceString name) => library.find(name);
   Element lookup(SourceString name) => localLookup(name);
 
   Element add(Element newElement) {
     throw "Cannot add an element to a library scope";
   }
 
   String toString() => 'LibraryScope($library)';
 }