Use Shadow DOM to display fallback content for images

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 249 matching lines @@
             newImage = document.fetcher()->fetchImage(request);
 
         if (!newImage && !pageIsBeingDismissed(&document))
             crossSiteOrCSPViolationOccured(imageSourceURL);
         else
             clearFailedLoadURL();
     } else if (!imageSourceURL.isNull()) {
         // Fire an error event if the url string is not empty, but the KURL is.
         m_hasPendingErrorEvent = true;
         errorEventSender().dispatchEventSoon(this);
+    } else {
+        noImageResourceToLoad();
     }
 
+
     ImageResource* oldImage = m_image.get();
     if (newImage != oldImage) {
         sourceImageChanged();
 
         if (m_hasPendingLoadEvent) {
             loadEventSender().cancelEvent(this);
             m_hasPendingLoadEvent = false;
         }
 
         // Cancel error events that belong to the previous load, which is now cancelled by changing the src attribute.
@@ skipping 40 matching lines @@
         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.
     if (m_pendingTask) {
         m_pendingTask->clearLoader();
         m_pendingTask.clear();
     }
 
     KURL url = imageSourceToKURL(imageSourceURL);
-    if (imageSourceURL.isNull() || url.isNull() || shouldLoadImmediately(url, loadType)) {
+    if ((!imageSourceURL.isNull() && url.isNull()) || shouldLoadImmediately(url, loadType)) {

[esprehn, 2014/09/05 00:47:52]

Why did you change this?

[rhogan, 2014/09/08 19:52:42]

This allows images with no src="" to go through the image loading process. When
they error out we can invoke the fallback content.

         doUpdateFromElement(DoNotBypassMainWorldCSP, updateBehavior);
         return;
     }
     enqueueImageLoadingMicroTask(updateBehavior);
 }
 
 KURL ImageLoader::imageSourceToKURL(AtomicString imageSourceURL) const
 {
     KURL url;
 
     // Don't load images for inactive documents. We don't want to slow down the
     // raw HTML parsing case by loading images we don't intend to display.
     Document& document = m_element->document();
     if (!document.isActive())
         return url;
 
     // Do not load any image if the 'src' attribute is missing or if it is
     // an empty string.
     if (!imageSourceURL.isNull() && !stripLeadingAndTrailingHTMLSpaces(imageSourceURL).isEmpty())
         url = document.completeURL(sourceURI(imageSourceURL));
     return url;
 }
 
 bool ImageLoader::shouldLoadImmediately(const KURL& url, LoadType loadType) const
 {
     return (m_loadingImageDocument
         || isHTMLObjectElement(m_element)
         || isHTMLEmbedElement(m_element)
         || url.protocolIsData()
-        || memoryCache()->resourceForURL(url)
+        || !element()->document().frame()

[esprehn, 2014/09/05 00:47:52]

What are you checking here? I think you mean document().isActive() ?

[rhogan, 2014/09/08 19:52:43]

When creating the MicroTask there's an
ASSERT(loader->element()->document().frame()); in shouldBypassMainWorldCSP().

+        || (!url.isNull() && memoryCache()->resourceForURL(url))
         || loadType == ForceLoadImmediately);
 }
 
 void ImageLoader::notifyFinished(Resource* resource)
 {
     WTF_LOG(Timers, "ImageLoader::notifyFinished %p; m_hasPendingLoadEvent=%d",
         this, m_hasPendingLoadEvent);
 
     ASSERT(m_failedLoadURL.isEmpty());
     ASSERT(resource == m_image.get());
@@ skipping 193 matching lines @@
 }
 
 #if ENABLE(OILPAN)
 ImageLoader::ImageLoaderClientRemover::~ImageLoaderClientRemover()
 {
     m_loader.willRemoveClient(m_client);
 }
 #endif
 
 }