Add link preload as=document support

third_party/WebKit/Source/core/loader/DocumentLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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 183 matching lines @@
         break;
     case Resource::TextTrack:
         resource = RawResource::fetchTextTrack(request, fetcher());
         break;
     case Resource::ImportResource:
         resource = RawResource::fetchImport(request, fetcher());
         break;
     case Resource::Raw:
         resource = RawResource::fetch(request, fetcher());
         break;
+    case Resource::MainResource:
+        resource = RawResource::fetchMainResource(request, fetcher(), m_substituteData);
+        break;
     default:
         ASSERT_NOT_REACHED();
     }
 
     if (resource)
         fetcher()->preloadStarted(resource);
     return resource;
 }
 
 void DocumentLoader::didRedirect(const KURL& oldURL, const KURL& newURL)
@@ skipping 517 matching lines @@
 {
     m_writer = createWriterFor(init, mimeType(), m_writer ? m_writer->encoding() : emptyAtom, true, ForceSynchronousParsing);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 DEFINE_WEAK_IDENTIFIER_MAP(DocumentLoader);
 
 } // namespace blink