Refactor BeforeInstallPromptEvent to use ScriptPromiseProperty

Source/modules/app_banner/AppBannerController.cpp

Index: Source/modules/app_banner/AppBannerController.cpp
diff --git a/Source/modules/app_banner/AppBannerController.cpp b/Source/modules/app_banner/AppBannerController.cpp
index af8b67f11f5c43cf8ccff7711fa76374464bbd6b..47af8985a0a765ee29cc6c2481d8c5defb0b4c8f 100644
--- a/Source/modules/app_banner/AppBannerController.cpp
+++ b/Source/modules/app_banner/AppBannerController.cpp
@@ -6,11 +6,14 @@
 #include "modules/app_banner/AppBannerController.h"
 
 #include "core/EventTypeNames.h"
+#include "core/dom/Document.h"
 #include "core/frame/DOMWindow.h"
 #include "core/frame/LocalFrame.h"
+#include "modules/app_banner/AppBannerCallbacks.h"
 #include "modules/app_banner/BeforeInstallPromptEvent.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "public/platform/WebVector.h"
+#include "public/platform/modules/app_banner/WebAppBannerClient.h"
 #include "public/platform/modules/app_banner/WebAppBannerPromptReply.h"
 
 namespace blink {
@@ -24,9 +27,13 @@ void AppBannerController::willShowInstallBannerPrompt(int requestId, WebAppBanne
     for (const WebString& platform : platforms)
         wtfPlatforms.append(platform);
 
+    RefPtrWillBeRawPtr<BeforeInstallPromptEvent> event = BeforeInstallPromptEvent::create(EventTypeNames::beforeinstallprompt, frame->document(), wtfPlatforms, requestId, client);
+    WebAppBannerCallbacks* callbacks = new AppBannerCallbacks(event->userChoiceProperty());
+    client->registerBannerCallbacks(requestId, callbacks);
+
     // dispatchEvent() returns whether the default behavior can happen. In other
     // words, it returns false if preventDefault() was called.
-    *reply = frame->domWindow()->dispatchEvent(BeforeInstallPromptEvent::create(EventTypeNames::beforeinstallprompt, wtfPlatforms, requestId, client))
+    *reply = frame->domWindow()->dispatchEvent(event)
         ? WebAppBannerPromptReply::None : WebAppBannerPromptReply::Cancel;
 }