Merge 95074

Source/WebCore/rendering/RenderScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 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 46 matching lines @@
     } else if (this->orientation() == HorizontalScrollbar)
         width = this->width();
     else
         height = this->height();
 
     setFrameRect(IntRect(0, 0, width, height));
 }
 
 RenderScrollbar::~RenderScrollbar()
 {
-    ASSERT(m_parts.isEmpty());
+    if (!m_parts.isEmpty()) {
+        // When a scrollbar is detached from its parent (causing all parts removal) and 
+        // ready to be destroyed, its destruction can be delayed because of RefPtr
+        // maintained in other classes such as EventHandler (m_lastScrollbarUnderMouse).
+        // Meanwhile, we can have a call to updateScrollbarPart which recreates the 
+        // scrollbar part. So, we need to destroy these parts since we don't want them
+        // to call on a destroyed scrollbar. See webkit bug 68009.
+        updateScrollbarParts(true);
+    }
 }
 
 RenderBox* RenderScrollbar::owningRenderer() const
 {
     if (m_owningFrame) {
         RenderBox* currentRenderer = m_owningFrame->ownerRenderer();
         return currentRenderer;
     }
     return m_owner;
 }
@@ skipping 280 matching lines @@
 int RenderScrollbar::minimumThumbLength()
 {
     RenderScrollbarPart* partRenderer = m_parts.get(ThumbPart);
     if (!partRenderer)
         return 0;    
     partRenderer->layout();
     return orientation() == HorizontalScrollbar ? partRenderer->width() : partRenderer->height();
 }
 
 }