Harmony: implement Math.sign.

src/harmony-math.js

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-// Flags: --allow-natives-syntax
+'use strict';
 
-"use strict";
-
-function f(a, b) {
-  return g("c", "d");
+// ES6 draft 09-27-13, section 20.2.2.28.
+function MathSign(x) {
+  if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
+  if (x > 0) return 1;
+  if (x < 0) return -1;
+  if (x === 0) return x;
+  return NAN;
 }
 
-function g(a, b) {
-  g.constructor.apply(this, arguments);
+
+function ExtendMath() {
+  %CheckIsBootstrapping();
+
+  // Set up the non-enumerable functions on the Math object.
+  InstallFunctions($Math, DONT_ENUM, $Array(
+    "sign", MathSign
+  ));
 }
 
-g.constructor = function(a, b) {
-  assertEquals("c", a);
-  assertEquals("d", b);
-}
-
-f("a", "b");
-f("a", "b");
-%OptimizeFunctionOnNextCall(f);
-f("a", "b");
-g.x = "deopt";
-f("a", "b");
+ExtendMath();