Allow preload scanners to be disabled by Settings.

Source/core/html/parser/HTMLPreloadScanner.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
  * Copyright (C) 2010 Google Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 460 matching lines @@
     FloatSize initialViewport(documentParameters->mediaValues->viewportHeight(), documentParameters->mediaValues->viewportWidth());
     PageScaleConstraints constraints = description.resolve(initialViewport, documentParameters->defaultViewportMinWidth);
     MediaValuesCached* cachedMediaValues = static_cast<MediaValuesCached*>(documentParameters->mediaValues.get());
     cachedMediaValues->setViewportHeight(constraints.layoutSize.height());
     cachedMediaValues->setViewportWidth(constraints.layoutSize.width());
 }
 
 template<typename Token>
 void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString& source, PreloadRequestStream& requests)
 {
+    if (!m_documentParameters->doHtmlPreloadScanning)
+        return;
+
     // Disable preload for documents with AppCache.
     if (m_isAppCacheEnabled)
         return;
 
     // http://crbug.com/434230 Disable preload for documents with CSP <meta> tags
     if (m_isCSPEnabled)
         return;
 
     switch (token.type()) {
     case HTMLToken::Character: {
@@ skipping 129 matching lines @@
         m_token.clear();
     }
 
     preloader->takeAndPreload(requests);
 }
 
 CachedDocumentParameters::CachedDocumentParameters(Document* document, PassRefPtr<MediaValues> givenMediaValues)
 {
     ASSERT(isMainThread());
     ASSERT(document);
+    doHtmlPreloadScanning = !document->settings() || document->settings()->doHtmlPreloadScanning();
     if (givenMediaValues)
         mediaValues = givenMediaValues;
     else
         mediaValues = MediaValuesCached::create(*document);
     ASSERT(mediaValues->isSafeToSendToAnotherThread());
     defaultViewportMinWidth = document->viewportDefaultMinWidth();
     viewportMetaZeroValuesQuirk = document->settings() && document->settings()->viewportMetaZeroValuesQuirk();
     viewportMetaEnabled = document->settings() && document->settings()->viewportMetaEnabled();
 }
 
 }