Enable srcset support in HTMLImageElement

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 440 matching lines @@
     // FIXME: Switch all callers of styleResolverChanged to these or better ones and then make them
     // do something smarter.
     void removedStyleSheet(StyleSheet*, StyleResolverUpdateType type = RecalcStyleDeferred) { styleResolverChanged(type); }
     void addedStyleSheet(StyleSheet*, StyleResolverUpdateType type = RecalcStyleDeferred) { styleResolverChanged(type); }
     void modifiedStyleSheet(StyleSheet*, StyleResolverUpdateType type = RecalcStyleDeferred) { styleResolverChanged(type); }
 
     void didAccessStyleResolver();
 
     void evaluateMediaQueryList();
 
-    // Never returns 0.

[do-not-use, 2013/09/12 08:23:53]

This was according to coding style:
http://www.chromium.org/blink/coding-style#TOC-Comments

+    // Never returns 0
     FormController* formController();
     Vector<String> formElementsState() const;
     void setStateForNewFormElements(const Vector<String>&);
 
-    FrameView* view() const; // can be NULL
-    Frame* frame() const { return m_frame; } // can be NULL
-    Page* page() const; // can be NULL
-    Settings* settings() const; // can be NULL
+    FrameView* view() const; // can be null
+    Frame* frame() const { return m_frame; } // can be null
+    Page* page() const; // can be null
+    Settings* settings() const; // can be null
+
+    float devicePixelRatio() const;
 
     PassRefPtr<Range> createRange();
 
     PassRefPtr<NodeIterator> createNodeIterator(Node* root, ExceptionState&);
     PassRefPtr<NodeIterator> createNodeIterator(Node* root, unsigned whatToShow, ExceptionState&);
     PassRefPtr<NodeIterator> createNodeIterator(Node* root, unsigned whatToShow, PassRefPtr<NodeFilter>, ExceptionState&);
     PassRefPtr<NodeIterator> createNodeIterator(Node* root, unsigned whatToShow, PassRefPtr<NodeFilter>, bool expandEntityReferences, ExceptionState&);
 
     PassRefPtr<TreeWalker> createTreeWalker(Node* root, ExceptionState&);
     PassRefPtr<TreeWalker> createTreeWalker(Node* root, unsigned whatToShow, ExceptionState&);
@@ skipping 952 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == documentInternal();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h