Check DisplayItemCient aliveness in cached subsequences

third_party/WebKit/Source/core/layout/LayoutView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 943 matching lines @@
     if (!m_compositor)
         m_compositor = adoptPtr(new PaintLayerCompositor(*this));
 
     return m_compositor.get();
 }
 
 void LayoutView::setIsInWindow(bool isInWindow)
 {
     if (m_compositor)
         m_compositor->setIsInWindow(isInWindow);
+#if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
+    // We don't invalidate layers during document detach(), so must clear the should-keep-alive

[chrishtr, 2016/06/18 08:49:57]

Does this need to be true any more now that we use cache generations?

[Xianzhu, 2016/06/18 17:41:30]

This doesn't affect cache correctness, but is only related to aliveness
tracking. Because when a document is detached, LayoutObjects are deleted before
PaintLayers, without this code we would crash when LayoutObjects were deleted
because they were still under shouldKeepAlive control of the ancestor
PaintLayers. 

+    // DisplayItemClients which may be deleted before the layers being subsequence owners.
+    if (!isInWindow && layer())
+        layer()->endShouldKeepAliveAllClientsRecursive();
+#endif
 }
 
 IntervalArena* LayoutView::intervalArena()
 {
     if (!m_intervalArena)
         m_intervalArena = IntervalArena::create();
     return m_intervalArena.get();
 }
 
 bool LayoutView::backgroundIsKnownToBeOpaqueInRect(const LayoutRect&) const
@@ skipping 62 matching lines @@
     // ASSERT(!frame()->isMainFrame()) here. All main frame scrolling should
     // be handled by the ViewportScrollCallback.
 
     if (!frameView())
         return ScrollResult(false, false, delta.width(), delta.height());
 
     return frameView()->getScrollableArea()->userScroll(granularity, delta);
 }
 
 } // namespace blink