Return null when no promise/reason is given in PromiseRejectionEvent

Source/bindings/core/v8/custom/V8PromiseRejectionEventCustom.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "bindings/core/v8/V8PromiseRejectionEvent.h"
+
+#include "bindings/core/v8/ScriptPromise.h"
+#include "bindings/core/v8/ScriptState.h"
+#include "bindings/core/v8/ScriptValue.h"
+#include "bindings/core/v8/V8Binding.h"
+
+namespace blink {
+
+void V8PromiseRejectionEvent::promiseAttributeGetterCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    v8::Isolate* isolate = info.GetIsolate();
+    PromiseRejectionEvent* event = V8PromiseRejectionEvent::toImpl(info.Holder());
+    ScriptPromise promise = event->promise(ScriptState::current(isolate));
+    if (promise.isEmpty()) {
+        v8SetReturnValue(info, v8::Null(isolate));
+        return;
+    }
+
+    v8SetReturnValue(info, promise.v8Value());
+}
+
+} // namespace blink