Collect closure functions in isolate

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 5f721a3cf5de9fc0655976ed3c53d083facda334..3906e77dabaa68f6efa07e161b643713d7f718ee 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -665,6 +665,12 @@ class Isolate : public BaseIsolate {
   // Handle service messages until we are told to resume execution.
   void PauseEventHandler();
 
+  void AddClosureFunction(const Function& function) const;
+  RawFunction* LookupClosureFunction(const Function& parent,
+                                     intptr_t token_pos) const;
+  intptr_t FindClosureIndex(const Function& needle) const;
+  RawFunction* ClosureFunctionFromIndex(intptr_t idx) const;
+
   bool is_service_isolate() const { return is_service_isolate_; }
 
   static void KillAllIsolates(LibMsgId msg_id);