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

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index f0e77968eb48fb6135ff9a8636a4dac6adbd18ad..720c06524d09a92fa3bbe037a4cab06ffb6c462f 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -768,7 +768,8 @@ bool Debug::CompileDebuggerScript(Isolate* isolate, int index) {
     isolate->ComputeLocation(&computed_location);
     Handle<Object> message = MessageHandler::MakeMessageObject(
         isolate, "error_loading_debugger", &computed_location,
-        Vector<Handle<Object> >::empty(), Handle<JSArray>());
+        Vector<Handle<Object> >::empty(), Handle<JSObject>(),
+        Handle<JSArray>());
     DCHECK(!isolate->has_pending_exception());
     Handle<Object> exception;
     if (maybe_exception.ToHandle(&exception)) {
@@ -1262,17 +1263,6 @@ bool Debug::IsBreakOnException(ExceptionBreakType type) {
 }
 
 
-bool Debug::PromiseHasRejectHandler(Handle<JSObject> promise) {
-  Handle<JSFunction> fun = Handle<JSFunction>::cast(
-      JSObject::GetDataProperty(isolate_->js_builtins_object(),
-                                isolate_->factory()->NewStringFromStaticChars(
-                                    "PromiseHasRejectHandler")));
-  Handle<Object> result =
-      Execution::Call(isolate_, fun, promise, 0, NULL).ToHandleChecked();
-  return result->IsTrue();
-}
-
-
 void Debug::PrepareStep(StepAction step_action,
                         int step_count,
                         StackFrame::Id frame_id) {
@@ -2501,7 +2491,8 @@ MaybeHandle<Object> Debug::MakeAsyncTaskEvent(Handle<JSObject> task_event) {
 }
 
 
-void Debug::OnThrow(Handle<Object> exception, bool uncaught) {
+void Debug::OnThrow(Handle<Object> exception, Handle<Object> promise,
+                    bool uncaught) {
   if (in_debug_scope() || ignore_events()) return;
   // Temporarily clear any scheduled_exception to allow evaluating
   // JavaScript from the debug event handler.
@@ -2511,7 +2502,7 @@ void Debug::OnThrow(Handle<Object> exception, bool uncaught) {
     scheduled_exception = handle(isolate_->scheduled_exception(), isolate_);
     isolate_->clear_scheduled_exception();
   }
-  OnException(exception, uncaught, isolate_->GetPromiseOnStackOnThrow());
+  OnException(exception, uncaught, promise);
   if (!scheduled_exception.is_null()) {
     isolate_->thread_local_top()->scheduled_exception_ = *scheduled_exception;
   }
@@ -2527,8 +2518,12 @@ void Debug::OnPromiseReject(Handle<JSObject> promise, Handle<Object> value) {
 
 void Debug::OnException(Handle<Object> exception, bool uncaught,
                         Handle<Object> promise) {
-  if (promise->IsJSObject()) {
-    uncaught |= !PromiseHasRejectHandler(Handle<JSObject>::cast(promise));
+  if (!uncaught && promise->IsJSObject()) {
+    Handle<Object> has_reject_handler;
+    ASSIGN_RETURN_ON_EXCEPTION_VALUE(
+        isolate_, has_reject_handler,
+        Execution::PromiseHasRejectHandler(isolate_, promise), /* void */);
+    uncaught = has_reject_handler->IsFalse();
   }
   // Bail out if exception breaks are not active
   if (uncaught) {