Don't change Document load progress in any page dismissal events.

third_party/WebKit/Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 2355 matching lines @@
             m_frame->loader().stopAllLoaders();
     }
 
     removeAllEventListenersRecursively();
     implicitOpen(ForceSynchronousParsing);
     if (ScriptableDocumentParser* parser = scriptableDocumentParser())
         parser->setWasCreatedByScript(true);
 
     if (m_frame)
         m_frame->loader().didExplicitOpen();
-    if (m_loadEventProgress != LoadEventInProgress && m_loadEventProgress != UnloadEventInProgress)
+    if (m_loadEventProgress != LoadEventInProgress && pageDismissalEventBeingDispatched() == NoDismissal)
         m_loadEventProgress = LoadEventNotRun;
 }
 
 void Document::detachParser()
 {
     if (!m_parser)
         return;
     m_parser->detach();
     m_parser.clear();
 }
@@ skipping 3367 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().string().utf8().data());
 }
 #endif