Async/await catch prediction for "the synchronous case"

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index a9b75a9fcb5fc2827eb7e32ec6be55e253974113..95c300f3a948fea72c49eda74ec084c9f6a655ee 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -673,8 +673,14 @@ class Isolate {
   // Push and pop a promise and the current try-catch handler.
   void PushPromise(Handle<JSObject> promise);
   void PopPromise();
+
+  // Return the relevant Promise that a throw/rejection pertains to, based
+  // on the contents of the Promise stack
   Handle<Object> GetPromiseOnStackOnThrow();
 
+  // Heuristically guess whether a Promise is handled by user catch handler
+  bool PromiseHasUserDefinedRejectHandler(Handle<Object> promise);
+
   class ExceptionScope {
    public:
     // Scope currently can only be used for regular exceptions,