Protect documents from deletion when their onload removes them

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 4044 matching lines @@
 {
     ASSERT(!scriptableDocumentParser() || !m_parser->isParsing());
     ASSERT(!scriptableDocumentParser() || m_readyState != Loading);
     setParsing(false);
     if (!m_documentTiming.domContentLoadedEventStart)
         m_documentTiming.domContentLoadedEventStart = monotonicallyIncreasingTime();
     dispatchEvent(Event::create(eventNames().DOMContentLoadedEvent, true, false));
     if (!m_documentTiming.domContentLoadedEventEnd)
         m_documentTiming.domContentLoadedEventEnd = monotonicallyIncreasingTime();
 
+    // The loader's finishedParsing() method may invoke script that causes this object to
+    // be dereferenced (when this document is in an iframe and the onload causes the iframe's src to change).
+    // Keep it alive until we are done.
+    RefPtr<Document> protect(this);

[abarth-chromium, 2013/07/22 18:06:24]

Why doesn't this issue occur with HTML documents?  Presumably the
HTMLDocumentParser holds a reference to the Document.  Perhaps the
XMLDocumentParser should do the same?  Is the XMLDocumentParser prepared for its
|document| to be garbage after calling this function?

+
     if (RefPtr<Frame> f = frame()) {
         // FrameLoader::finishedParsing() might end up calling Document::implicitClose() if all
         // resource loads are complete. HTMLObjectElements can start loading their resources from
         // post attach callbacks triggered by recalcStyle().  This means if we parse out an <object>
         // tag and then reach the end of the document without updating styles, we might not have yet
         // started the resource load and might fire the window load event too early.  To avoid this
         // we force the styles to be up to date before calling FrameLoader::finishedParsing().
         // See https://bugs.webkit.org/show_bug.cgi?id=36864 starting around comment 35.
         updateStyleIfNeeded();
 
@@ skipping 1076 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore