Remove clips where we can show that they are unnecessary.

Source/core/rendering/RenderBlock.h

Index: Source/core/rendering/RenderBlock.h
diff --git a/Source/core/rendering/RenderBlock.h b/Source/core/rendering/RenderBlock.h
index ac22f2955b9854e1ec626c362c2bb953bf3afb6f..47687f020d2bf964c91f031f16d7b56f18909ca6 100644
--- a/Source/core/rendering/RenderBlock.h
+++ b/Source/core/rendering/RenderBlock.h
@@ -545,6 +545,7 @@ protected:
 
 public:
     void computeOverflow(LayoutUnit oldClientAfterEdge, bool recomputeFloats = false);
+    virtual void addVisualOverflow(const LayoutRect&, VisualOverflowClipBehavior) OVERRIDE FINAL;
 protected:
     virtual void addOverflowFromChildren();
     void addOverflowFromFloats();
@@ -1228,7 +1229,7 @@ public:
     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)
@@ -1256,11 +1257,11 @@ public:
         {
             return std::max<LayoutUnit>(-block->marginAfter(), 0);
         }
-        
+
         MarginValues m_margins;
         LayoutUnit m_paginationStrut;
         LayoutUnit m_pageLogicalOffset;
-        
+
         RootInlineBox* m_lineGridBox;
 
         RootInlineBox* m_lineBreakToAvoidWidow;
@@ -1268,6 +1269,8 @@ public:
         bool m_shouldBreakAtLineToAvoidWidow : 1;
         bool m_discardMarginBefore : 1;
         bool m_discardMarginAfter : 1;
+
+        LayoutRect m_contentsVisualOverflowRect;
      };
 
 protected:
@@ -1296,7 +1299,7 @@ private:
 };
 
 inline RenderBlock* toRenderBlock(RenderObject* object)
-{ 
+{
     ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isRenderBlock());
     return static_cast<RenderBlock*>(object);
 }