Add @JSName annotation for native fields and methods.

sdk/lib/_internal/compiler/implementation/elements/elements.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 elements;
 
 import 'dart:uri';
 
 // TODO(ahe): Rename prefix to 'api' when VM bug is fixed.
 import '../../compiler.dart' as api_e;
@@ skipping 337 matching lines @@
     if (enclosingElement != null && !isTopLevel()) {
       String holderName = enclosingElement.name != null
           ? enclosingElement.name.slowToString()
           : '${enclosingElement.kind}?';
       return '$kind($holderName#${nameText})';
     } else {
       return '$kind(${nameText})';
     }
   }
 
-  bool _isNative = false;
-  void setNative() { _isNative = true; }
-  bool isNative() => _isNative;
+  String _nativeName = null;
+  bool isNative() => _nativeName != null;
+  String nativeName() => _nativeName;
+  /// Marks this element as a native element.
+  void setNative(String name) { _nativeName = name; }
 
   FunctionElement asFunctionElement() => null;
 
   static bool isInvalid(Element e) => e == null || e.isErroneous();
 
   bool isAbstract(Compiler compiler) => modifiers.isAbstract();
 }
 
 /**
  * Represents an unresolvable or duplicated element.
@@ skipping 1009 matching lines @@
   }
 }
 
 abstract class ClassElement extends ScopeContainerElement
     implements TypeDeclarationElement {
   final int id;
   InterfaceType type;
   DartType supertype;
   DartType defaultClass;
   Link<DartType> interfaces;
-  SourceString nativeName;
+  SourceString nativeTagInfo;
   int supertypeLoadState;
   int resolutionState;
 
   // backendMembers are members that have been added by the backend to simplify
   // compilation. They don't have any user-side counter-part.
   Link<Element> backendMembers = const Link<Element>();
 
   Link<DartType> allSupertypes;
 
   // Lazily applied patch of class members.
@@ skipping 316 matching lines @@
    * account.
    */
   bool isSubclassOf(ClassElement cls) {
     for (ClassElement s = this; s != null; s = s.superclass) {
       if (identical(s, cls)) return true;
     }
     return false;
   }
 
   bool isInterface() => false;
-  bool isNative() => nativeName != null;
+  bool isNative() => nativeTagInfo != null;
   int get hashCode => id;
 
   Scope buildScope() => new ClassScope(enclosingElement.buildScope(), this);
 
   Link<DartType> get allSupertypesAndSelf {
     return allSupertypes.prepend(new InterfaceType(this));
   }
 
   String toString() {
     if (origin != null) {
@@ skipping 337 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }