Remove clips where we can show that they are unnecessary.

Source/core/rendering/RenderBlock.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 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.
@@ skipping 527 matching lines @@
 
     virtual bool hasLineIfEmpty() const;
     
     bool simplifiedLayout();
     virtual void simplifiedNormalFlowLayout();
 
     void setDesiredColumnCountAndWidth(int, LayoutUnit);
 
 public:
     void computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats = false);
+    virtual void addVisualOverflow(const LayoutRect&, VisualOverflowClipBehavior) OVERRIDE FINAL;
 protected:
     virtual void addOverflowFromChildren();
     void addOverflowFromFloats();
     void addOverflowFromPositionedObjects();
     void addOverflowFromBlockChildren();
     void addOverflowFromInlineChildren();
     void addVisualOverflowFromTheme();
 
     virtual void addFocusRingRects(Vector<IntRect>&, const LayoutPoint& additionalOffset, const RenderLayerModelObject* paintContainer = 0) OVERRIDE;
 
@@ skipping 663 matching lines @@
         bool m_horizontalWritingMode;
         const RenderBlock* m_renderer;
 
         friend void RenderBlock::createFloatingObjects();
     };
 
     // Allocated only when some of these fields have non-default values
     struct RenderBlockRareData {
         WTF_MAKE_NONCOPYABLE(RenderBlockRareData); WTF_MAKE_FAST_ALLOCATED;
     public:
-        RenderBlockRareData(const RenderBlock* block) 
+        RenderBlockRareData(const RenderBlock* block)
             : m_margins(positiveMarginBeforeDefault(block), negativeMarginBeforeDefault(block), positiveMarginAfterDefault(block), negativeMarginAfterDefault(block))
             , m_paginationStrut(0)
             , m_pageLogicalOffset(0)
             , m_lineGridBox(0)
             , m_lineBreakToAvoidWidow(0)
             , m_shouldBreakAtLineToAvoidWidow(false)
             , m_discardMarginBefore(false)
             , m_discardMarginAfter(false)
         { 
         }
 
         static LayoutUnit positiveMarginBeforeDefault(const RenderBlock* block)
         { 
             return std::max<LayoutUnit>(block->marginBefore(), 0);
         }
         static LayoutUnit negativeMarginBeforeDefault(const RenderBlock* block)
         { 
             return std::max<LayoutUnit>(-block->marginBefore(), 0);
         }
         static LayoutUnit positiveMarginAfterDefault(const RenderBlock* block)
         {
             return std::max<LayoutUnit>(block->marginAfter(), 0);
         }
         static LayoutUnit negativeMarginAfterDefault(const RenderBlock* block)
         {
             return std::max<LayoutUnit>(-block->marginAfter(), 0);
         }
-        
+
         MarginValues m_margins;
         LayoutUnit m_paginationStrut;
         LayoutUnit m_pageLogicalOffset;
-        
+
         RootInlineBox* m_lineGridBox;
 
         RootInlineBox* m_lineBreakToAvoidWidow;
         OwnPtr<ExclusionShapeInsideInfo> m_shapeInsideInfo;
         bool m_shouldBreakAtLineToAvoidWidow : 1;
         bool m_discardMarginBefore : 1;
         bool m_discardMarginAfter : 1;
+
+        LayoutRect m_contentsVisualOverflowRect;
      };
 
 protected:
 
     OwnPtr<FloatingObjects> m_floatingObjects;
     OwnPtr<RenderBlockRareData> m_rareData;
 
     RenderObjectChildList m_children;
     RenderLineBoxList m_lineBoxes;   // All of the root line boxes created for this block flow.  For example, <div>Hello<br>world.</div> will have two total lines for the <div>.
 
     mutable signed m_lineHeight : 27;
     unsigned m_hasMarginBeforeQuirk : 1; // Note these quirk values can't be put in RenderBlockRareData since they are set too frequently.
     unsigned m_hasMarginAfterQuirk : 1;
     unsigned m_beingDestroyed : 1;
     unsigned m_hasMarkupTruncation : 1;
     unsigned m_hasBorderOrPaddingLogicalWidthChanged : 1;
 
     // RenderRubyBase objects need to be able to split and merge, moving their children around
     // (calling moveChildTo, moveAllChildrenTo, and makeChildrenNonInline).
     friend class RenderRubyBase;
     friend class LineWidth; // Needs to know FloatingObject
 
 private:
     // Used to store state between styleWillChange and styleDidChange
     static bool s_canPropagateFloatIntoSibling;
 };
 
 inline RenderBlock* toRenderBlock(RenderObject* object)
-{ 
+{
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderBlock());
     return static_cast<RenderBlock*>(object);
 }
 
 inline const RenderBlock* toRenderBlock(const RenderObject* object)
 { 
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderBlock());
     return static_cast<const RenderBlock*>(object);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toRenderBlock(const RenderBlock*);
 
 #ifndef NDEBUG
 // These structures are used by PODIntervalTree for debugging purposes.
 template <> struct ValueToString<int> {
     static String string(const int value);
 };
 template<> struct ValueToString<RenderBlock::FloatingObject*> {
     static String string(const RenderBlock::FloatingObject*);
 };
 #endif
 
 } // namespace WebCore
 
 #endif // RenderBlock_h