Report promise reject with no handler (behind a flag).

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index a92554ebe3d19135e3671e29669fd83005e4170b..5bdf2179da30c8c212bc636b3340864f096e847a 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -778,12 +778,20 @@ class Isolate {
 
   // Promote a scheduled exception to pending. Asserts has_scheduled_exception.
   Object* PromoteScheduledException();
+
+  Handle<JSMessageObject> CreateMessage(
+      Handle<Object> exception, MessageLocation* location,
+      Handle<JSObject> promise = Handle<JSObject>());
+
   void DoThrow(Object* exception, MessageLocation* location);
   // Checks if exception should be reported and finds out if it's
   // caught externally.
   bool ShouldReportException(bool* can_be_caught_externally,
                              bool catchable_by_javascript);
 
+  void ReportPromiseReject(Handle<JSObject> promise, Handle<Object> exception,
+                           MessageLocation* location);
+
   // Attempts to compute the current source location, storing the
   // result in the target out parameter.
   void ComputeLocation(MessageLocation* target);