Never return a Dart_Handle on a dart::Class from the embedding API.

runtime/include/dart_api.h

Index: runtime/include/dart_api.h
diff --git a/runtime/include/dart_api.h b/runtime/include/dart_api.h
index 80fc69bebafedac67d945ef02e21808d7fa33669..5c10137ccab02fd84326c92db677039bd6ba6280 100755
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -1174,18 +1174,6 @@ DART_EXPORT bool Dart_IsClosure(Dart_Handle object);
  */
 DART_EXPORT Dart_Handle Dart_InstanceGetType(Dart_Handle instance);
 
-/**
- * TODO(asiva): Deprecate this method once all use cases have switched
- *              to using Dart_InstanceGetType
- * Gets the class for some Dart language object.
- *
- * \param instance Some Dart object.
- *
- * \return If no error occurs, the class is returned. Otherwise an
- *   error handle is returned.
- */
-DART_EXPORT Dart_Handle Dart_InstanceGetClass(Dart_Handle instance);
-
 
 /*
  * =============================