Fix runtimeType for strings, integers and double: return their interface type.

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 325 matching lines @@
   _invoke(reflectee, functionName, arguments, argumentNames)
       native 'InstanceMirror_invoke';
 
   _invokeGetter(reflectee, getterName)
       native 'InstanceMirror_invokeGetter';
 
   _invokeSetter(reflectee, setterName, value)
       native 'InstanceMirror_invokeSetter';
 
   static _computeType(reflectee)
-      native 'Object_runtimeType';
+      native 'InstanceMirror_computeType';
 }
 
 class _LocalClosureMirrorImpl extends _LocalInstanceMirrorImpl
     implements ClosureMirror {
   _LocalClosureMirrorImpl(reflectee) : super(reflectee);
 
   MethodMirror _function;
   MethodMirror get function {
     if (_function == null) {
       _function = _computeFunction(reflectee);
@@ skipping 964 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }