Do not recompute client{width,height} the long way in paddingBoxRect

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 c04b779229b4aec27c5f0643998969c8c9029ff6..63fca12eefbb2a77040ca1b7aed1daeae75990ea 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -166,7 +166,7 @@ public:
     void setFrameRect(const LayoutRect& rect) { m_frameRect = rect; }
 
     LayoutRect borderBoxRect() const { return LayoutRect(LayoutPoint(), size()); }
-    LayoutRect paddingBoxRect() const { return LayoutRect(borderLeft(), borderTop(), contentWidth() + paddingLeft() + paddingRight(), contentHeight() + paddingTop() + paddingBottom()); }
+    LayoutRect paddingBoxRect() const { return LayoutRect(borderLeft(), borderTop(), clientWidth(), clientHeight()); }
     IntRect pixelSnappedBorderBoxRect() const { return IntRect(IntPoint(), m_frameRect.pixelSnappedSize()); }
     virtual IntRect borderBoundingBox() const override final { return pixelSnappedBorderBoxRect(); }