Hide native Date implementation in function context.

src/third_party/fdlibm/fdlibm.js

 // The following is adapted from fdlibm (http://www.netlib.org/fdlibm),
 //
 // ====================================================
 // Copyright (C) 1993-2004 by Sun Microsystems, Inc. All rights reserved.
 //
 // Developed at SunSoft, a Sun Microsystems, Inc. business.
 // Permission to use, copy, modify, and distribute this
 // software is freely granted, provided that this notice
 // is preserved.
 // ====================================================
 //
 // The original source code covered by the above license above has been
 // modified significantly by Google Inc.
 // Copyright 2014 the V8 project authors. All rights reserved.
 //
 // The following is a straightforward translation of fdlibm routines
 // by Raymond Toy (rtoy@google.com).
 
 // Double constants that do not have empty lower 32 bits are found in fdlibm.cc
 // and exposed through kMath as typed array. We assume the compiler to convert
 // from decimal to binary accurately enough to produce the intended values.
 // kMath is initialized to a Float64Array during genesis and not writable.
 // rempio2result is used as a container for return values of %RemPiO2. It is
 // initialized to a two-element Float64Array during genesis.
 
-"use strict";
-
 var kMath;
 var rempio2result;
 
 (function() {
+  
+"use strict";
 
 const INVPIO2 = kMath[0];
 const PIO2_1  = kMath[1];
 const PIO2_1T = kMath[2];
 const PIO2_2  = kMath[3];
 const PIO2_2T = kMath[4];
 const PIO2_3  = kMath[5];
 const PIO2_3T = kMath[6];
 const PIO4    = kMath[32];
 const PIO4LO  = kMath[33];
@@ skipping 955 matching lines @@
 
   // log2(ax) = (ss + ...) * 2 / (3 * log(2)) = n + dp_h + z_h + z_l
   var t = n;
   var t1 = %_ConstructDouble(%_DoubleHi(((z_h + z_l) + dp_h) + t), 0);
   var t2 = z_l - (((t1 - t) - dp_h) - z_h);
 
   // t1 + t2 = log2(ax), sum up because we do not care about extra precision.
   return t1 + t2;
 }
 
-InstallFunctions($Math, DONT_ENUM, $Array(
+//-------------------------------------------------------------------
+
+%CheckIsBootstrapping();
+
+InstallFunctions(global.Math, DONT_ENUM, $Array(
   "cos", MathCos,
   "sin", MathSin,
   "tan", MathTan,
   "sinh", MathSinh,
   "cosh", MathCosh,
   "log10", MathLog10,
   "log2", MathLog2,
   "log1p", MathLog1p,
   "expm1", MathExpm1
 ));
 
 %SetInlineBuiltinFlag(MathSin);
 %SetInlineBuiltinFlag(MathCos);
 
 })();