Sort class IDs before training AppJIT snapshots

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 9aff87019e0f837eb99222f2ec70e7c76f2a1bfd..4db93630fc3f533ed4bbf7c2e78767134dd3d34a 100644
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -3279,6 +3279,14 @@ Dart_CreateAppAOTSnapshotAsBlobs(uint8_t** vm_snapshot_data_buffer,
 
 
 /**
+ * Sorts the class-ids in depth first traversal order of the inheritance
+ * tree.  This is a costly operation, but it can make method dispatch
+ * more efficient and is done before writing snapshots.
+ */
+DART_EXPORT void Dart_SortClasses();
+
+
+/**
  *  Creates a snapshot that caches compiled code and type feedback for faster
  *  startup and quicker warmup in a subsequent process.
  *