Harmony: fix spec violation in Math.cosh.

src/harmony-math.js

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 41 matching lines @@
   if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
   // Idempotent for NaN, +/-0 and +/-Infinity.
   if (x === 0 || !NUMBER_IS_FINITE(x)) return x;
   return (MathExp(x) - MathExp(-x)) / 2;
 }
 
 
 // ES6 draft 09-27-13, section 20.2.2.12.
 function MathCosh(x) {
   if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
-  // Idempotent for NaN and +/-Infinity.
-  if (!NUMBER_IS_FINITE(x)) return x;
+  if (!NUMBER_IS_FINITE(x)) return MathAbs(x);
   return (MathExp(x) + MathExp(-x)) / 2;
 }
 
 
 // ES6 draft 09-27-13, section 20.2.2.33.
 function MathTanh(x) {
   if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
   // Idempotent for +/-0.
   if (x === 0) return x;
   // Returns +/-1 for +/-Infinity.
@@ skipping 94 matching lines @@
     "asinh", MathAsinh,
     "acosh", MathAcosh,
     "atanh", MathAtanh,
     "log10", MathLog10,
     "log2", MathLog2,
     "hypot", MathHypot
   ));
 }
 
 ExtendMath();