[turbofan] Use builtin inlining mechanism for Math.floor.

src/math.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 "use strict";
 
 // This file relies on the fact that the following declarations have been made
 // in runtime.js:
 // var $Object = global.Object;
 
@@ skipping 333 matching lines @@
   "asinh", MathAsinh,
   "acosh", MathAcosh,
   "atanh", MathAtanh,
   "hypot", MathHypot,
   "fround", MathFroundJS,
   "clz32", MathClz32,
   "cbrt", MathCbrt
 ));
 
 %SetInlineBuiltinFlag(MathCeil);
+%SetInlineBuiltinFlag(MathFloor);
 %SetInlineBuiltinFlag(MathRandom);
 
 // Keep reference to original values of some global properties.  This
 // has the added benefit that the code in this file is isolated from
 // changes to these properties.
 $abs = MathAbs;
 $exp = MathExp;
 $floor = MathFloor;
 $max = MathMax;
 $min = MathMin;
 
 })();