Images from content:url() aren't loading if the alt attribute is present

Source/core/html/HTMLImageElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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 75 matching lines @@
     bool canContainRangeEndPoint() const override { return false; }
 
     void addClient(ImageLoaderClient* client) { imageLoader().addClient(client); }
     void removeClient(ImageLoaderClient* client) { imageLoader().removeClient(client); }
 
     const AtomicString imageSourceURL() const override;
 
     HTMLFormElement* formOwner() const override;
     void formRemovedFromTree(const Node& formRoot);
     virtual void ensureFallbackContent();
+    virtual void ensureFallbackForGeneratedContent();
     virtual void ensurePrimaryContent();
 
     // CanvasImageSource implementation
     PassRefPtr<Image> getSourceImageForCanvas(SourceImageStatus*) const override;
     bool wouldTaintOrigin(SecurityOrigin*) const override;
     FloatSize elementSize() const override;
     FloatSize defaultDestinationSize() const override;
     const KURL& sourceURL() const override;
     bool isOpaque() const override;
 
@@ skipping 61 matching lines @@
     unsigned m_elementCreatedByParser : 1;
     // Intrinsic sizing is viewport dependant if the 'w' descriptor was used for the picked resource.
     unsigned m_intrinsicSizingViewportDependant : 1;
     unsigned m_useFallbackContent : 1;
     unsigned m_isFallbackImage : 1;
 };
 
 } // namespace blink
 
 #endif // HTMLImageElement_h