Make ImageLoader have at most one pending error event on EventSender

third_party/WebKit/Source/core/loader/ImageLoader.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010 Apple Inc. All rights
  * reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 255 matching lines @@
     params.SetCrossOriginAccessControl(
         element.GetDocument().GetSecurityOrigin(), cross_origin);
   }
 
   if (client_hints_preferences.ShouldSendResourceWidth() &&
       isHTMLImageElement(element))
     params.SetResourceWidth(toHTMLImageElement(element).GetResourceWidth());
 }
 
 inline void ImageLoader::DispatchErrorEvent() {
+  // There can be cases where DispatchErrorEvent() is called when there is
+  // already a scheduled error event for the previous load attempt.
+  // In such cases we cancel the previous event and then re-schedule a new
+  // error event here. crbug.com/722500
+  if (has_pending_error_event_)
+    ErrorEventSender().CancelEvent(this);
+
   has_pending_error_event_ = true;
   ErrorEventSender().DispatchEventSoon(this);
 }
 
 inline void ImageLoader::CrossSiteOrCSPViolationOccurred(
     AtomicString image_source_url) {
   failed_load_url_ = image_source_url;
 }
 
 inline void ImageLoader::ClearFailedLoadURL() {
@@ skipping 386 matching lines @@
   if (GetElement()->GetDocument().GetFrame())
     DispatchLoadEvent();
 
   // Only consider updating the protection ref-count of the Element immediately
   // before returning from this function as doing so might result in the
   // destruction of this ImageLoader.
   UpdatedHasPendingEvent();
 }
 
 void ImageLoader::DispatchPendingErrorEvent() {
-  // Currently this if condition is needed because there can be multiple
-  // in-flight error event tasks and we process only the first here.
-  // crbug.com/722500
-  // TODO(hiroshige): Replace this with |CHECK(has_pending_load_event_)|.
-  if (!has_pending_error_event_)
-    return;
+  CHECK(has_pending_error_event_);
   has_pending_error_event_ = false;
 
   if (GetElement()->GetDocument().GetFrame())
     GetElement()->DispatchEvent(Event::Create(EventTypeNames::error));
 
   // Only consider updating the protection ref-count of the Element immediately
   // before returning from this function as doing so might result in the
   // destruction of this ImageLoader.
   UpdatedHasPendingEvent();
 }
@@ skipping 21 matching lines @@
   }
   if (delay_until_image_notify_finished_) {
     delay_until_image_notify_finished_->DocumentChanged(
         element_->GetDocument());
   }
   ClearFailedLoadURL();
   ClearImage();
 }
 
 }  // namespace blink