Generate mock libraries and assert that helpers are non-null.

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 507 matching lines @@
     Iterable matches = unusedClasses.where(predicate);
     matches.toList().forEach((c) => enqueueClass(c, cause));
   }
 
   onFirstNativeClass() {
     staticUse(name) {
       backend.enqueue(
           world, backend.findHelper(name), compiler.globalDependencies);
     }
 
-    staticUse('dynamicFunction');
-    staticUse('dynamicSetMetadata');
     staticUse('defineProperty');
     staticUse('toStringForNativeObject');
     staticUse('hashCodeForNativeObject');
     staticUse('convertDartClosureToJS');
     addNativeExceptions();
   }
 
   addNativeExceptions() {
     enqueueUnusedClassesMatching((classElement) {
         // TODO(sra): Annotate exception classes in dart:html.
@@ skipping 653 matching lines @@
     LiteralString jsCode = nativeBody.asLiteralString();
     builder.push(new HForeign.statement(
         js.js.statementTemplateYielding(
             new js.LiteralStatement(jsCode.dartString.slowToString())),
         <HInstruction>[],
         new SideEffects(),
         null,
         backend.dynamicType));
   }
 }