[es6] Implement spec compliant ToPrimitive in the runtime.

test/mjsunit/harmony/to-number.js

+// Copyright 2015 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.
+
+// Flags: --allow-natives-syntax
+
+assertEquals(1, %ToNumber(1));
+assertEquals(1, %_ToNumber(1));
+
+assertEquals(.5, %ToNumber(.5));
+assertEquals(.5, %_ToNumber(.5));
+
+assertEquals(0, %ToNumber(null));
+assertEquals(0, %_ToNumber(null));
+
+assertEquals(1, %ToNumber(true));
+assertEquals(1, %_ToNumber(true));
+
+assertEquals(0, %ToNumber(false));
+assertEquals(0, %_ToNumber(false));
+
+assertEquals(NaN, %ToNumber(undefined));
+assertEquals(NaN, %_ToNumber(undefined));
+
+assertEquals(-1, %ToNumber("-1"));
+assertEquals(-1, %_ToNumber("-1"));
+assertEquals(123, %ToNumber("123"));
+assertEquals(123, %_ToNumber("123"));
+assertEquals(NaN, %ToNumber("random text"));
+assertEquals(NaN, %_ToNumber("random text"));
+
+assertThrows(function() { %ToNumber(Symbol.toPrimitive) }, TypeError);
+assertThrows(function() { %_ToNumber(Symbol.toPrimitive) }, TypeError);
+
+var a = { toString: function() { return 54321 }};
+assertEquals(54321, %ToNumber(a));
+assertEquals(54321, %_ToNumber(a));
+
+var b = { valueOf: function() { return 42 }};
+assertEquals(42, %ToNumber(b));
+assertEquals(42, %_ToNumber(b));
+
+var c = {
+  toString: function() { return "x"},
+  valueOf: function() { return 123 }
+};
+assertEquals(123, %ToNumber(c));
+assertEquals(123, %_ToNumber(c));
+
+var d = {
+  [Symbol.toPrimitive]: function(hint) {
+    assertEquals("number", hint);
+    return 987654321;
+  }
+};
+assertEquals(987654321, %ToNumber(d));
+assertEquals(987654321, %_ToNumber(d));