avoid ambiguous overload for operator= in FrameView.h

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@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
@@ skipping 201 matching lines @@
 
     void updateLayoutAndStyleForPainting();
     void updateLayoutAndStyleIfNeededRecursive();
 
     void invalidateTreeIfNeededRecursive();
 
     void incrementVisuallyNonEmptyCharacterCount(unsigned);
     void incrementVisuallyNonEmptyPixelCount(const IntSize&);
     void setIsVisuallyNonEmpty() { m_isVisuallyNonEmpty = true; }
     void enableAutoSizeMode(const IntSize& minSize, const IntSize& maxSize);
-    void disableAutoSizeMode() { m_autoSizeInfo = 0; }
+    void disableAutoSizeMode() { m_autoSizeInfo.clear(); }
 
     void forceLayout(bool allowSubtree = false);
     void forceLayoutForPagination(const FloatSize& pageSize, const FloatSize& originalPageSize, float maximumShrinkFactor);
 
     bool scrollToFragment(const KURL&);
     bool scrollToAnchor(const String&);
     void maintainScrollPositionAtAnchor(Node*);
     void scrollElementToRect(Element*, const IntRect&);
     void scrollContentsIfNeededRecursive();
 
@@ skipping 302 matching lines @@
         m_view->setCanInvalidatePaintDuringPerformLayout(m_originalValue);
     }
 private:
     FrameView* m_view;
     bool m_originalValue;
 };
 
 } // namespace blink
 
 #endif // FrameView_h