Remove Isolate::top_exit_frame_info()

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
diff --git a/runtime/vm/isolate.h b/runtime/vm/isolate.h
index 5c05638d41b8d958155fd0526f203b4406ddea04..86575f01ffb0c2a0b0df8e0976ad7be890524609 100644
--- a/runtime/vm/isolate.h
+++ b/runtime/vm/isolate.h
@@ -188,10 +188,6 @@ class Isolate : public BaseIsolate {
   ObjectStore* object_store() const { return object_store_; }
   void set_object_store(ObjectStore* value) { object_store_ = value; }
 
-  uword top_exit_frame_info() const {
-    return mutator_thread_->top_exit_frame_info();
-  }
-
   ApiState* api_state() const { return api_state_; }
   void set_api_state(ApiState* value) { api_state_ = value; }