Fix crash when removing contents from a document having multiple bodies

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

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 27 matching lines @@
     : LayoutBlock(nullptr)
     , m_scrollableArea(scrollableArea)
     , m_scrollbar(scrollbar)
     , m_part(part)
 {
     ASSERT(m_scrollableArea);
 }
 
 LayoutScrollbarPart::~LayoutScrollbarPart()
 {
+#if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
+    // We may not have invalidated the painting layer for now, but the
+    // scrollable area will invalidate during paint invalidation.
+    endShouldKeepAlive();
+#endif
 }
 
 static void recordScrollbarPartStats(Document& document, ScrollbarPart part)
 {
     switch (part) {
     case BackButtonStartPart:
     case ForwardButtonStartPart:
     case BackButtonEndPart:
     case ForwardButtonEndPart:
         UseCounter::count(document, UseCounter::CSSSelectorPseudoScrollbarButton);
@@ skipping 159 matching lines @@
 }
 
 LayoutRect LayoutScrollbarPart::visualRect() const
 {
     // This returns the combined bounds of all scrollbar parts, which is sufficient for correctness
     // but not as tight as it could be.
     return m_scrollableArea->visualRectForScrollbarParts();
 }
 
 } // namespace blink