Allow preload scanners to be disabled by Settings.

Source/core/html/parser/HTMLPreloadScanner.h

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 33 matching lines @@
 class HTMLParserOptions;
 class HTMLTokenizer;
 class SegmentedString;
 
 struct CORE_EXPORT CachedDocumentParameters {
     static PassOwnPtr<CachedDocumentParameters> create(Document* document, PassRefPtr<MediaValues> mediaValues = nullptr)
     {
         return adoptPtr(new CachedDocumentParameters(document, mediaValues));
     }
 
+    bool doHtmlPreloadScanning;
     RefPtr<MediaValues> mediaValues;
     Length defaultViewportMinWidth;
     bool viewportMetaZeroValuesQuirk;
     bool viewportMetaEnabled;
 
 private:
     CachedDocumentParameters(Document*, PassRefPtr<MediaValues>);
 };
 
 class TokenPreloadScanner {
@@ skipping 77 matching lines @@
 private:
     TokenPreloadScanner m_scanner;
     SegmentedString m_source;
     HTMLToken m_token;
     OwnPtr<HTMLTokenizer> m_tokenizer;
 };
 
 }
 
 #endif