Make Pageshow event asynchronous in EventQueueScope

third_party/WebKit/Source/core/frame/LocalDOMWindow.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 406 matching lines @@
 void LocalDOMWindow::DocumentWasClosed() {
   DispatchWindowLoadEvent();
   EnqueuePageshowEvent(kPageshowEventNotPersisted);
   if (pending_state_object_)
     EnqueuePopstateEvent(std::move(pending_state_object_));
 }
 
 void LocalDOMWindow::EnqueuePageshowEvent(PageshowEventPersistence persisted) {
   // FIXME: https://bugs.webkit.org/show_bug.cgi?id=36334 Pageshow event needs
   // to fire asynchronously.  As per spec pageshow must be triggered
   // asynchronously.  However to be compatible with other browsers blink fires

[tkent, 2017/04/13 01:26:16]

Did you check behavior of latest versions of other browsers?

If some other browsers dispatch it asynchronously, it should be safe to switch
to unconditional asynchronous dispatch.

[tkent, 2017/04/13 06:19:14]

We had offline discussion.
It's too difficult to reproduce synchronous pageshow dispatch even in Chrome.
So, investigating other browsers behavior is also too hard.
We may go ahead with the current approach.  lgtm

-  // pageshow synchronously.
+  // pageshow synchronously unless we are in EventQueueScope.
+  if (ScopedEventQueue::Instance()->ShouldQueueEvents() && document_) {

[yosin_UTC9, 2017/04/12 10:08:03]

Nice finding. I've not known
|(ScopedEventQueue::Instance()->ShouldQueueEvents()|.
(^_^)b

+      EnqueueWindowEvent(
+        PageTransitionEvent::Create(EventTypeNames::pageshow, persisted));
+    return;
+  }
   DispatchEvent(
       PageTransitionEvent::Create(EventTypeNames::pageshow, persisted),
       document_.Get());
 }
 
 void LocalDOMWindow::EnqueueHashchangeEvent(const String& old_url,
                                             const String& new_url) {
   EnqueueWindowEvent(HashChangeEvent::Create(old_url, new_url));
 }
 
@@ skipping 1240 matching lines @@
   DOMWindow::Trace(visitor);
   Supplementable<LocalDOMWindow>::Trace(visitor);
 }
 
 DEFINE_TRACE_WRAPPERS(LocalDOMWindow) {
   visitor->TraceWrappers(custom_elements_);
   DOMWindow::TraceWrappers(visitor);
 }
 
 }  // namespace blink