Added basic client hints support.

Source/core/fetch/ImageResource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007 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
@@ skipping 407 matching lines @@
     Resource::error(status);
     notifyObservers();
 }
 
 void ImageResource::responseReceived(const ResourceResponse& response, PassOwnPtr<WebDataConsumerHandle> handle)
 {
     if (m_loadingMultipartContent && m_data)
         finishOnePart();
     else if (response.isMultipart())
         m_loadingMultipartContent = true;
-    if (RuntimeEnabledFeatures::clientHintsDprEnabled()) {
+    if (RuntimeEnabledFeatures::clientHintsEnabled()) {
         m_devicePixelRatioHeaderValue = response.httpHeaderField("DPR").toFloat(&m_hasDevicePixelRatioHeaderValue);
         if (!m_hasDevicePixelRatioHeaderValue || m_devicePixelRatioHeaderValue <= 0.0) {
             m_devicePixelRatioHeaderValue = 1.0;
             m_hasDevicePixelRatioHeaderValue = false;
         }
     }
     Resource::responseReceived(response, handle);
 }
 
 void ImageResource::decodedSizeChanged(const blink::Image* image, int delta)
@@ skipping 115 matching lines @@
     if (node && isHTMLImageElement(node)) {
         const AtomicString& urlString = toHTMLImageElement(node)->imageSourceURL();
         KURL url = node->document().completeURL(urlString);
         imageForContainer->setURL(url);
     }
 
     return imageForContainer.get();
 }
 
 } // namespace blink