1. Dynamic compute the main closure that needs to be run by the main isolate

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 51b96038a57f0bb74c5798640461f0216667a545..2e8b8648097332cbdc1483f794d49cc2af4ff02b 100644
--- a/runtime/include/dart_api.h
+++ b/runtime/include/dart_api.h
@@ -1611,6 +1611,20 @@ DART_EXPORT Dart_Handle Dart_NewDouble(double value);
  */
 DART_EXPORT Dart_Handle Dart_DoubleValue(Dart_Handle double_obj, double* value);
 
+/**
+ * Returns a closure of top level function 'function_name' in the exported
+ * namespace of specified 'library'. If a top level function 'function_name'
+ * does not exist, looks for a top level getter 'function_name' and invokes
+ * it and returns the object returned by the getter.
+ *
+ * \param library Library object
+ * \param function_name Name of the top level function
+ *
+ * \return A valid Dart instance if no error occurs during the operation.
+ */
+DART_EXPORT Dart_Handle Dart_GetClosure(Dart_Handle library,
+                                        Dart_Handle function_name);
+
 
 /*
  * ========