Move remaining helpers to BackendHelpers

pkg/compiler/lib/src/js_backend/no_such_method_registry.dart

 // Copyright (c) 2015, 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 js_backend;
 
 /**
  * Categorizes `noSuchMethod` implementations.
  *
  * If user code includes `noSuchMethod` implementations, type inference is
@@ skipping 150 matching lines @@
       return NsmCategory.THROWING;
     } else {
       otherImpls.add(element);
       return NsmCategory.OTHER;
     }
   }
 
   bool _isDefaultNoSuchMethodImplementation(FunctionElement element) {
     ClassElement classElement = element.enclosingClass;
     return classElement == _compiler.coreClasses.objectClass
-        || classElement == _backend.jsInterceptorClass
-        || classElement == _backend.jsNullClass;
+        || classElement == _backend.helpers.jsInterceptorClass
+        || classElement == _backend.helpers.jsNullClass;
   }
 
   bool _hasForwardingSyntax(FunctionElement element) {
     // At this point we know that this is signature-compatible with
     // Object.noSuchMethod, but it may have more than one argument as long as
     // it only has one required argument.
     String param = element.parameters.first.name;
     Statement body = element.node.body;
     Expression expr;
     if (body is Return && body.isArrowBody) {
@@ skipping 35 matching lines @@
       if (body.statements.nodes.head is ExpressionStatement) {
         ExpressionStatement stmt = body.statements.nodes.head;
         return stmt.expression is Throw;
       }
     }
     return false;
   }
 }
 
 enum NsmCategory { DEFAULT, THROWING, OTHER }