Fix Math.log10 implementation for 1 - Number.EPSILON.

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.
 // ====================================================
@@ skipping 868 matching lines @@
     k -= 54;
     x *= TWO54;
     hx = %_DoubleHi(x);
     lx = %_DoubleLo(x);
   }
 
   // Infinity or NaN.
   if (hx >= 0x7ff00000) return x;
 
   k += (hx >> 20) - 1023;
-  var i = (k & 0x80000000) >> 31;
+  var i = (k & 0x80000000) >>> 31;
   hx = (hx & 0x000fffff) | ((0x3ff - i) << 20);
   var y = k + i;
   x = %_ConstructDouble(hx, lx);
 
   var z = y * LOG10_2LO + IVLN10 * %_MathLogRT(x);
   return z + y * LOG10_2HI;
 }
 
 
 // ES6 draft 09-27-13, section 20.2.2.22.
@@ skipping 121 matching lines @@
   "log10", MathLog10,
   "log2", MathLog2,
   "log1p", MathLog1p,
   "expm1", MathExpm1
 ]);
 
 %SetInlineBuiltinFlag(MathSin);
 %SetInlineBuiltinFlag(MathCos);
 
 })();