Switch arguments to const Length references for performance

Source/platform/LengthBox.h

 /*
     Copyright (C) 1999 Lars Knoll (knoll@kde.org)
     Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
     Copyright (c) 2012, Google 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 35 matching lines @@
     }
 
     LengthBox(int v)
         : m_left(Length(v, Fixed))
         , m_right(Length(v, Fixed))
         , m_top(Length(v, Fixed))
         , m_bottom(Length(v, Fixed))
     {
     }
 
-    LengthBox(Length t, Length r, Length b, Length l)
+    LengthBox(const Length& t, const Length& r, const Length& b, const Length& l)
         : m_left(l)
         , m_right(r)
         , m_top(t)
         , m_bottom(b)
     {
     }
 
     LengthBox(int t, int r, int b, int l)
         : m_left(Length(l, Fixed))
         , m_right(Length(r, Fixed))
@@ skipping 33 matching lines @@
     // Must be public for SET_VAR in RenderStyle.h
     Length m_left;
     Length m_right;
     Length m_top;
     Length m_bottom;
 };
 
 } // namespace WebCore
 
 #endif // LengthBox_h