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

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index bda34bdfacacbb369f5e8db2b18d03c6f38b1ec7..ad544f580e138aade3dbd45004e7265be1b78080 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -2068,6 +2068,17 @@ Local<String> Message::Get() const {
 }
 
 
+v8::Handle<v8::Promise> Message::GetPromise() const {
+  i::Handle<i::JSMessageObject> message =
+      i::Handle<i::JSMessageObject>::cast(Utils::OpenHandle(this));
+  i::Object* promise = message->promise();
+  if (promise->IsUndefined()) return v8::Handle<v8::Promise>();
+  i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
+  i::Handle<i::JSObject> promise_handle(i::JSObject::cast(promise), isolate);
+  return Utils::PromiseToLocal(promise_handle);
+}
+
+
 ScriptOrigin Message::GetScriptOrigin() const {
   i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
   i::Handle<i::JSMessageObject> message =
@@ -5971,6 +5982,20 @@ Local<Promise> Promise::Then(Handle<Function> handler) {
 }
 
 
+bool Promise::HasRejectHandler() {
+  i::Handle<i::JSObject> promise = Utils::OpenHandle(this);
+  i::Isolate* isolate = promise->GetIsolate();
+  LOG_API(isolate, "Promise::HasRejectHandler");
+  ENTER_V8(isolate);
+  EXCEPTION_PREAMBLE(isolate);
+  i::Handle<i::Object> result;
+  has_pending_exception = !i::Execution::PromiseHasRejectHandler(
+                               isolate, promise).ToHandle(&result);
+  EXCEPTION_BAILOUT_CHECK(isolate, false);
+  return result->BooleanValue();
+}
+
+
 bool v8::ArrayBuffer::IsExternal() const {
   return Utils::OpenHandle(this)->is_external();
 }