Oilpan: extend tracing over WebFrame trees.

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 233 matching lines @@
 
     // Prevent window.open(url) -- eg window.open("about:blank") -- from blowing away results
     // from a subsequent window.document.open / window.document.write call.
     // Canceling redirection here works for all cases because document.open
     // implicitly precedes document.write.
     m_frame->navigationScheduler().cancel();
 }
 
 void FrameLoader::clear()
 {
-    // clear() is called during (Local)Frame finalization and when creating
-    // a new Document within it (DocumentLoader::createWriterFor().)
+    // clear() is called during (Local)Frame detachment or when
+    // reusing a FrameLoader by putting a new Document within it
+    // (DocumentLoader::ensureWriter().)
     if (m_stateMachine.creatingInitialEmptyDocument())
         return;
 
     m_frame->editor().clear();
     m_frame->document()->cancelParsing();
     m_frame->document()->prepareForDestruction();
     m_frame->document()->removeFocusedElementOfSubtree(m_frame->document());
     m_frame->selection().prepareForDestruction();
     m_frame->eventHandler().clear();
     if (m_frame->view())
@@ skipping 1210 matching lines @@
     // FIXME: We need a way to propagate sandbox flags to out-of-process frames.
     Frame* parentFrame = m_frame->tree().parent();
     if (parentFrame && parentFrame->isLocalFrame())
         flags |= toLocalFrame(parentFrame)->document()->sandboxFlags();
     if (FrameOwner* frameOwner = m_frame->owner())
         flags |= frameOwner->sandboxFlags();
     return flags;
 }
 
 } // namespace blink