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

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index ac25e48853080f384600f0417e9073aba50daa69..38bdf84e6222bdde039f04aaf5f22b42924ffa8e 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -180,6 +180,7 @@ enum BindingFlags {
   V(PROMISE_CHAIN_INDEX, JSFunction, promise_chain)                            \
   V(PROMISE_CATCH_INDEX, JSFunction, promise_catch)                            \
   V(PROMISE_THEN_INDEX, JSFunction, promise_then)                              \
+  V(PROMISE_HAS_REJECT_HANDLER_INDEX, JSFunction, promise_has_reject_handler)  \
   V(TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX, JSFunction,                         \
     to_complete_property_descriptor)                                           \
   V(DERIVED_HAS_TRAP_INDEX, JSFunction, derived_has_trap)                      \
@@ -377,6 +378,7 @@ class Context: public FixedArray {
     PROMISE_CHAIN_INDEX,
     PROMISE_CATCH_INDEX,
     PROMISE_THEN_INDEX,
+    PROMISE_HAS_REJECT_HANDLER_INDEX,
     TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX,
     DERIVED_HAS_TRAP_INDEX,
     DERIVED_GET_TRAP_INDEX,