Refactor code for <img> size calculation during attach

Source/core/html/HTMLImageElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 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 147 matching lines @@
 
 void HTMLImageElement::attach(const AttachContext& context)
 {
     HTMLElement::attach(context);
 
     if (renderer() && renderer()->isImage() && !m_imageLoader.hasPendingBeforeLoadEvent()) {
         RenderImage* renderImage = toRenderImage(renderer());
         RenderImageResource* renderImageResource = renderImage->imageResource();
         if (renderImageResource->hasImage())
             return;
-        renderImageResource->setCachedImage(m_imageLoader.image());
 
         // If we have no image at all because we have no src attribute, set
         // image height and width for the alt text instead.
         if (!m_imageLoader.image() && !renderImageResource->cachedImage())
             renderImage->setImageSizeForAltText();
+        else
+            renderImageResource->setCachedImage(m_imageLoader.image());
+
     }
 }
 
 Node::InsertionNotificationRequest HTMLImageElement::insertedInto(ContainerNode* insertionPoint)
 {
     // m_form can be non-null if it was set in constructor.
     if (!m_form) {
         m_form = findFormAncestor();
         if (m_form)
             m_form->registerImgElement(this);
@@ skipping 175 matching lines @@
 
 Image* HTMLImageElement::imageContents()
 {
     if (!m_imageLoader.imageComplete())
         return 0;
 
     return m_imageLoader.image()->image();
 }
 
 }