Add proper API for creating private symbols wrt a library.

runtime/lib/mirrors_impl.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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection";
 
 // These values are allowed to be passed directly over the wire.
 bool _isSimpleValue(var value) {
@@ skipping 271 matching lines @@
   delegate(Invocation invocation) {
     if (_invokeOnClosure == null) {
       // TODO(ahe): This is a total hack.  We're using the mirror
       // system to access a private field in a different library.  For
       // some reason, that works.  On the other hand, calling a
       // private method does not work.
 
       _LocalInstanceMirrorImpl mirror =
           reflect(invocation);
       _invokeOnClosure = reflectClass(invocation.runtimeType)
-          .getField(const Symbol('_invokeOnClosure')).reflectee;
+          .getField(MirrorSystem.getSymbol('_invokeOnClosure', mirror.type.owner)).reflectee;
     }
     return _invokeOnClosure(reflectee, invocation);
   }
 
   String toString() => 'InstanceMirror on ${Error.safeToString(_reflectee)}';
 
   bool operator ==(other) {
     return other is _LocalInstanceMirrorImpl &&
            identical(_reflectee, other._reflectee);
   }
@@ skipping 1018 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }