Error event shouldn't fire when image is updated on environment changes.

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 102 matching lines @@
 
 ImageLoader::ImageLoader(Element* element)
     : m_element(element)
     , m_image(0)
     , m_derefElementTimer(this, &ImageLoader::timerFired)
     , m_hasPendingLoadEvent(false)
     , m_hasPendingErrorEvent(false)
     , m_imageComplete(true)
     , m_loadingImageDocument(false)
     , m_elementIsProtected(false)
+    , m_environmentChangeOnly(false)
     , m_highPriorityClientCount(0)
 {
     WTF_LOG(Timers, "new ImageLoader %p", this);
 }
 
 ImageLoader::~ImageLoader()
 {
     WTF_LOG(Timers, "~ImageLoader %p; m_hasPendingLoadEvent=%d, m_hasPendingErrorEvent=%d",
         this, m_hasPendingLoadEvent, m_hasPendingErrorEvent);
 
@@ skipping 168 matching lines @@
         // being queued to fire. Ensure this happens after beforeload is dispatched.
         if (newImage)
             newImage->addClient(this);
 
         if (oldImage)
             oldImage->removeClient(this);
     } else if (updateBehavior == UpdateSizeChanged && m_element->renderer() && m_element->renderer()->isImage()) {
         toRenderImage(m_element->renderer())->intrinsicSizeChanged();
     }
 
+    if (updateBehavior == UpdateSizeChanged)
+        m_environmentChangeOnly = true;

[Mike West, 2014/10/17 14:12:40]

You can drop the `if` and just assign the result of the comparison to the
variable.

+
     if (RenderImageResource* imageResource = renderImageResource())
         imageResource->resetAnimation();
 
     // 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::updateFromElement(UpdateFromElementBehavior updateBehavior, LoadType loadType)
 {
+    m_environmentChangeOnly = false;
     AtomicString imageSourceURL = m_element->imageSourceURL();
 
     if (updateBehavior == UpdateIgnorePreviousError)
         clearFailedLoadURL();
 
     if (!m_failedLoadURL.isEmpty() && imageSourceURL == m_failedLoadURL)
         return;
 
     // If we have a pending task, we have to clear it -- either we're
     // now loading immediately, or we need to reset the task's state.
@@ skipping 48 matching lines @@
     m_imageComplete = true;
     updateRenderer();
 
     if (!m_hasPendingLoadEvent)
         return;
 
     if (resource->errorOccurred()) {
         loadEventSender().cancelEvent(this);
         m_hasPendingLoadEvent = false;
 
-        m_hasPendingErrorEvent = true;
-        errorEventSender().dispatchEventSoon(this);
+        // The error event should not fire if the image data update is a result of environment change.
+        // https://html.spec.whatwg.org/multipage/embedded-content.html#the-img-element:the-img-element-55
+        if (!m_environmentChangeOnly) {
+            m_hasPendingErrorEvent = true;
+            errorEventSender().dispatchEventSoon(this);
+        }
 
         // 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();
         return;
     }
     if (resource->wasCanceled()) {
         m_hasPendingLoadEvent = false;
         // 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.
@@ skipping 170 matching lines @@
 }
 
 #if ENABLE(OILPAN)
 ImageLoader::ImageLoaderClientRemover::~ImageLoaderClientRemover()
 {
     m_loader.willRemoveClient(m_client);
 }
 #endif
 
 }