Add Blink support for showing image placeholders using range requests.

third_party/WebKit/Source/core/css/CSSImageValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "core/css/CSSImageValue.h"
 
 #include "core/css/CSSMarkup.h"
 #include "core/dom/Document.h"
 #include "core/fetch/FetchInitiatorTypeNames.h"
 #include "core/fetch/FetchRequest.h"
 #include "core/fetch/ImageResource.h"
 #include "core/fetch/ResourceFetcher.h"
+#include "core/frame/Settings.h"
 #include "core/loader/MixedContentChecker.h"
 #include "core/style/StyleFetchedImage.h"
 #include "core/style/StyleInvalidImage.h"
 #include "platform/CrossOriginAttributeValue.h"
 #include "platform/weborigin/KURL.h"
 #include "platform/weborigin/SecurityPolicy.h"
 
 namespace blink {
 
 CSSImageValue::CSSImageValue(const AtomicString& rawValue,
@@ skipping 18 matching lines @@
                          m_initiatorName.isEmpty()
                              ? FetchInitiatorTypeNames::css
                              : m_initiatorName);
     request.mutableResourceRequest().setHTTPReferrer(
         SecurityPolicy::generateReferrer(m_referrer.referrerPolicy,
                                          request.url(), m_referrer.referrer));
 
     if (crossOrigin != CrossOriginAttributeNotSet)
       request.setCrossOriginAccessControl(document.getSecurityOrigin(),
                                           crossOrigin);
+    if (document.settings() && document.settings()->fetchImagePlaceholders())
+      request.setAllowImagePlaceholder();
 
     if (ImageResource* cachedImage =
             ImageResource::fetch(request, document.fetcher()))
       m_cachedImage =
           StyleFetchedImage::create(cachedImage, document, request.url());
     else
       m_cachedImage = StyleInvalidImage::create(url());
   }
 
   return m_cachedImage.get();
@@ skipping 52 matching lines @@
 void CSSImageValue::reResolveURL(const Document& document) const {
   KURL url = document.completeURL(m_relativeURL);
   AtomicString urlString(url.getString());
   if (urlString == m_absoluteURL)
     return;
   m_absoluteURL = urlString;
   m_cachedImage.clear();
 }
 
 }  // namespace blink