Re-instantiate the mixed iframe block for M30.

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 461 matching lines @@
     if (frameLoader()->isLoadingMainFrame())
         newRequest.setFirstPartyForCookies(newRequest.url());
 
     // If we're fielding a redirect in response to a POST, force a load from origin, since
     // this is a common site technique to return to a page viewing some data that the POST
     // just modified.
     // Also, POST requests always load from origin, but this does not affect subresources.
     if (newRequest.cachePolicy() == UseProtocolCachePolicy && isPostOrRedirectAfterPost(newRequest, redirectResponse))
         newRequest.setCachePolicy(ReloadIgnoringCacheData);
 
-    Frame* top = m_frame->tree()->top();
-    if (top) {
-        if (!top->loader()->mixedContentChecker()->canDisplayInsecureContent(top->document()->securityOrigin(), newRequest.url())) {
+    Frame* parent = m_frame->tree()->parent();
+    if (parent) {
+        if (!parent->loader()->mixedContentChecker()->canRunInsecureContent(parent->document()->securityOrigin(), newRequest.url())) {
             cancelMainResourceLoad(ResourceError::cancelledError(newRequest.url()));
             return;
         }
     }
 
     setRequest(newRequest);
 
     if (redirectResponse.isNull())
         return;
 
@@ skipping 578 matching lines @@
 void DocumentLoader::replaceDocument(const String& source, Document* ownerDocument)
 {
     m_frame->loader()->stopAllLoaders();
     m_writer = createWriterFor(m_frame, ownerDocument, m_frame->document()->url(), mimeType(), m_writer ? m_writer->encoding() : "",  m_writer ? m_writer->encodingWasChosenByUser() : false, true);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 } // namespace WebCore