Refactor BeforeInstallPromptEvent to use ScriptPromiseProperty

Source/modules/app_banner/AppBannerCallbacks.cpp

Index: Source/modules/app_banner/AppBannerCallbacks.cpp
diff --git a/Source/modules/app_banner/AppBannerCallbacks.cpp b/Source/modules/app_banner/AppBannerCallbacks.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3da3c29a6dc5eda679dcbf57ec0be562efc53c17
--- /dev/null
+++ b/Source/modules/app_banner/AppBannerCallbacks.cpp
@@ -0,0 +1,20 @@
+// 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 "modules/app_banner/AppBannerCallbacks.h"
+
+namespace blink {
+
+AppBannerCallbacks::AppBannerCallbacks(UserChoiceProperty* userChoice)
+    : m_userChoice(userChoice)
+{
+}
+
+void AppBannerCallbacks::onSuccess(WebAppBannerPromptResult* result)
+{
+    m_userChoice->resolve(AppBannerPromptResult::take(adoptPtr(result)));
+}
+
+} // namespace blink