Move remaining helpers to BackendHelpers

pkg/compiler/lib/src/patch_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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 484 matching lines @@
     return hasJsInterop ? true : null;
   }
 
   @override
   void validate(Compiler compiler,
                 Element element,
                 MetadataAnnotation annotation,
                 ConstantValue constant) {
     JavaScriptBackend backend = compiler.backend;
     if (constant.getType(compiler.coreTypes).element !=
-        backend.jsAnnotationClass) {
+        backend.helpers.jsAnnotationClass) {
       compiler.reporter.internalError(annotation, 'Invalid @JS(...) annotation.');
     }
   }
 }
 
 /// Annotation handler for pre-resolution detection of `@patch` annotations.
 class PatchAnnotationHandler implements EagerAnnotationHandler<PatchVersion> {
   const PatchAnnotationHandler();
 
   PatchVersion getPatchVersion(MetadataAnnotation annotation) {
@@ skipping 172 matching lines @@
 
 class PatchVersion {
   final String tag;
 
   const PatchVersion(this.tag);
 
   bool isActive(String patchTag) => tag == null || tag == patchTag;
 
   String toString() => 'PatchVersion($tag)';
 }