Remove unused API.

dart/sdk/lib/_internal/compiler/implementation/native_handler.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 native;
 
 import 'dart:collection' show Queue;
 import 'dart2jslib.dart';
 import 'dart_types.dart';
 import 'elements/elements.dart';
@@ skipping 1027 matching lines @@
   Node node = listener.nodes.head;
   if (node != null
       && node.asIdentifier() != null
       && node.asIdentifier().source == 'native') {
     nativeTagInfo = node.asIdentifier().token.next.value;
     listener.popNode();
   }
   return nativeTagInfo;
 }
 
-bool isOverriddenMethod(FunctionElement element,
-                        ClassElement cls,
-                        NativeEmitter nativeEmitter) {
-  List<ClassElement> subtypes = nativeEmitter.subtypes[cls];
-  if (subtypes == null) return false;
-  for (ClassElement subtype in subtypes) {
-    if (subtype.lookupLocalMember(element.name) != null) return true;
-  }
-  return false;
-}
-
 final RegExp nativeRedirectionRegExp = new RegExp(r'^[a-zA-Z][a-zA-Z_$0-9]*$');
 
 void handleSsaNative(SsaBuilder builder, Expression nativeBody) {
   Compiler compiler = builder.compiler;
   FunctionElement element = builder.work.element;
   NativeEmitter nativeEmitter = builder.emitter.nativeEmitter;
   JavaScriptBackend backend = builder.backend;
 
   HInstruction convertDartClosure(Element parameter, FunctionType type) {
     HInstruction local = builder.localsHandler.readLocal(parameter);
@@ skipping 77 matching lines @@
     }
     LiteralString jsCode = nativeBody.asLiteralString();
     builder.push(new HForeign.statement(
         new js.LiteralStatement(jsCode.dartString.slowToString()),
         <HInstruction>[],
         new SideEffects(),
         null,
         backend.dynamicType));
   }
 }