Oilpan: extend tracing over WebFrame trees.

Source/core/frame/LocalFrame.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Simon Hausmann <hausmann@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  *                     2001 George Staikos <staikos@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov <ap@nypop.com>
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 256 matching lines @@
         ASSERT(fabs(originalSize.height()) > std::numeric_limits<float>::epsilon());
         float ratio = originalSize.width() / originalSize.height();
         resultSize.setHeight(floorf(expectedSize.height()));
         resultSize.setWidth(floorf(resultSize.height() * ratio));
     }
     return resultSize;
 }
 
 void LocalFrame::setDOMWindow(PassRefPtrWillBeRawPtr<LocalDOMWindow> domWindow)
 {
+    // Oilpan: setDOMWindow() cannot be used when finalizing. Which
+    // is acceptable as its actions are either not needed or handled
+    // by other means --
+    //
+    //  - FrameDestructionObserver::willDetachFrameHost() will have
+    //    signalled the Inspector frameWindowDiscarded() notifications.
+    //    We assume that all LocalFrames are detached, where that notification
+    //    will have been done.
+    //
+    //  - Calling LocalDOMWindow::reset() is not needed (called from
+    //    Frame::setDOMWindow().) The Member references it clears will now
+    //    die with the window. And the registered DOMWindowProperty instances that don't,
+    //    only keep a weak reference to this frame, so there's no need to be
+    //    explicitly notified that this frame is going away.
     if (m_domWindow) {
-        // Oilpan: the assumption is that FrameDestructionObserver::willDetachFrameHost()
-        // on LocalWindow will have signalled these frameWindowDiscarded() notifications.
-        //
-        // It is not invoked when finalizing the LocalFrame, as setDOMWindow() isn't
-        // performed (accessing the m_domWindow heap object is unsafe then.)
         console().messageStorage()->frameWindowDiscarded(m_domWindow.get());
         InspectorInstrumentation::frameWindowDiscarded(this, m_domWindow.get());
     }
     if (domWindow)
         script().clearWindowProxy();
     Frame::setDOMWindow(domWindow);
 }
 
 void LocalFrame::didChangeVisibilityState()
 {
@@ skipping 438 matching lines @@
 
     return curFrame;
 }
 
 void LocalFrame::setPagePopupOwner(Element& owner)
 {
     m_pagePopupOwner = &owner;
 }
 
 } // namespace blink