Handle LocalFrame being nestedly detached by subframe.

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 461 matching lines @@
 void FrameLoader::finishedParsing()
 {
     if (m_stateMachine.creatingInitialEmptyDocument())
         return;
 
     // This can be called from the LocalFrame's destructor, in which case we shouldn't protect ourselves
     // because doing so will cause us to re-enter the destructor when protector goes out of scope.
     // Null-checking the FrameView indicates whether or not we're in the destructor.
     RefPtrWillBeRawPtr<LocalFrame> protect(m_frame->view() ? m_frame.get() : nullptr);
 
-    m_progressTracker->finishedParsing();
+    if (m_progressTracker)

[Nate Chapin, 2015/08/17 17:01:58]

Is there any work that needs to be done in the frame-already-detached case? Can
we early-exit at the top of the function instead?

[sof, 2015/08/18 05:24:13]

It won't do any work before the detach check just below, so you could insert
another one at the top here.

This is related to #2 -- it seems preferable to head off repeated LocalFrame
detaches at the frame level, rather than at the auxiliary FrameLoader.

+        m_progressTracker->finishedParsing();
 
     if (client())
         client()->dispatchDidFinishDocumentLoad(m_documentLoader->isCommittedButEmpty());
 
     checkCompleted();
 
     if (!m_frame->view())
         return; // We are being destroyed by something checkCompleted called.
 
     // Check if the scrollbars are really needed for the content.
@@ skipping 1021 matching lines @@
     // FIXME: We need a way to propagate insecure requests policy flags to
     // out-of-process frames. For now, we'll always use default behavior.
     if (!parentFrame->isLocalFrame())
         return nullptr;
 
     ASSERT(toLocalFrame(parentFrame)->document());
     return toLocalFrame(parentFrame)->document()->insecureNavigationsToUpgrade();
 }
 
 } // namespace blink