Refactor avoidsFloats() to reflect CSS2.1 spec more clearly

Source/core/rendering/RenderBox.h

Index: Source/core/rendering/RenderBox.h
diff --git a/Source/core/rendering/RenderBox.h b/Source/core/rendering/RenderBox.h
index d84d104742fada5948a060a4424e297d3d11f98c..7618678f8aa247b80049243a905954588774cd2f 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -664,6 +664,8 @@ protected:
 
     void updateIntrinsicContentLogicalHeight(LayoutUnit intrinsicContentLogicalHeight) const { m_intrinsicContentLogicalHeight = intrinsicContentLogicalHeight; }
 
+    bool createsBlockFormattingContext() const;
+
 private:
     void updateShapeOutsideInfoAfterStyleChange(const RenderStyle&, const RenderStyle* oldStyle);
     void updateGridPositionAfterStyleChange(const RenderStyle*);