Call shutdown callback before the isolate is destroyed

runtime/vm/dart.cc

Index: runtime/vm/dart.cc
diff --git a/runtime/vm/dart.cc b/runtime/vm/dart.cc
index 300e5b31e75817fd6e61f19895f7121252861033..5cb465a7642e0d7e8793a6598d8204fa868a15b7 100644
--- a/runtime/vm/dart.cc
+++ b/runtime/vm/dart.cc
@@ -213,13 +213,12 @@ RawError* Dart::InitializeIsolate(const uint8_t* snapshot_buffer, void* data) {
 void Dart::ShutdownIsolate() {
   Isolate* isolate = Isolate::Current();
   void* callback_data = isolate->init_callback_data();
-  isolate->Shutdown();
-  delete isolate;
-
   Dart_IsolateShutdownCallback callback = Isolate::ShutdownCallback();
   if (callback != NULL) {
     (callback)(callback_data);
   }
+  isolate->Shutdown();
+  delete isolate;
 }