Revert of Issue FrameDestructionObserver::frameDestroyed() notification on detach.

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 188 matching lines @@
 
 LocalFrame::~LocalFrame()
 {
     // Verify that the FrameView has been cleared as part of detaching
     // the frame owner.
     ASSERT(!m_view);
 
 #if !ENABLE(OILPAN)
     // Oilpan: see setDOMWindow() comment why it is acceptable not to
     // mirror the non-Oilpan call below.
+    //
+    // Also, FrameDestructionObservers that live longer than this
+    // frame object keep weak references to the frame; those will be
+    // automatically cleared by the garbage collector. Hence, explicit
+    // frameDestroyed() notifications aren't needed.
     setDOMWindow(nullptr);
+
+    for (const auto& frameDestructionObserver : m_destructionObservers)
+        frameDestructionObserver->frameDestroyed();
 #endif
 }
 
 void LocalFrame::trace(Visitor* visitor)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_destructionObservers);
     visitor->trace(m_loader);
     visitor->trace(m_navigationScheduler);
     visitor->trace(m_view);
@@ skipping 56 matching lines @@
     script().clearForClose();
     ScriptForbiddenScope forbidScript;
     setView(nullptr);
     willDetachFrameHost();
     InspectorInstrumentation::frameDetachedFromParent(this);
     Frame::detach();
     // Clear the FrameLoader right here rather than during
     // finalization. Too late to access various heap objects at that
     // stage.
     m_loader.clear();
-
-    // Signal frame destruction here rather than in the destructor.
-    // Main motivation is to avoid being dependent on its exact timing (Oilpan.)
-    for (const auto& frameDestructionObserver : m_destructionObservers)
-        frameDestructionObserver->frameDestroyed();
 }
 
 SecurityContext* LocalFrame::securityContext() const
 {
     return document();
 }
 
 void LocalFrame::printNavigationErrorMessage(const Frame& targetFrame, const char* reason)
 {
     if (!targetFrame.isLocalFrame())
@@ skipping 518 matching lines @@
     // We detach the FrameView's custom scroll bars as early as
     // possible to prevent m_doc->detach() from messing with the view
     // such that its scroll bars won't be torn down.
     //
     // FIXME: We should revisit this.
     if (m_view)
         m_view->prepareForDetach();
 }
 
 } // namespace blink