Use precaching for more data: urls than just images.

Source/core/loader/FrameFetchContext.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 522 matching lines @@
     // In such cases a service worker ID could be retrieved from the document
     // loader of the frame.
     return frame()->loader().client()->serviceWorkerID(*frame()->loader().documentLoader());
 }
 
 bool FrameFetchContext::isMainFrame() const
 {
     return frame()->isMainFrame();
 }
 
-bool FrameFetchContext::hasSubstituteData() const
-{
-    return m_documentLoader && m_documentLoader->substituteData().isValid();
-}
-
 bool FrameFetchContext::defersLoading() const
 {
     return frame()->page()->defersLoading();
 }
 
 bool FrameFetchContext::isLoadComplete() const
 {
     return m_document && m_document->loadEventFinished();
 }
 
@@ skipping 118 matching lines @@
 }
 
 DEFINE_TRACE(FrameFetchContext)
 {
     visitor->trace(m_document);
     visitor->trace(m_documentLoader);
     FetchContext::trace(visitor);
 }
 
 } // namespace blink