Bug 143375

Originally, it is hidden in web pages because it causes Facebook's comment input. When landing Object.getOwnPropertySymbols, original issue is solved, so I think it's time to enable Symbols in web pages. And I suggest exposing only effective well-known symbols. Here's all well-known symbols. Specification Name [[Description]] Value and Purpose @@hasInstance "Symbol.hasInstance" A method that determines if a constructor object recognizes an object as one of the constructor’s instances. Called by the semantics of the instanceof operator. @@isConcatSpreadable "Symbol.isConcatSpreadable" A Boolean valued property that if true indicates that an object should be flattened to its array elements by Array.prototype.concat. @@iterator "Symbol.iterator" A method that returns the default Iterator for an object. Called by the semantics of the for-of statement. @@match "Symbol.match" A regular expression method that matches the regular expression against a string. Called by the String.prototype.match method. @@replace "Symbol.replace" A regular expression method that replaces matched substrings of a string. Called by the String.prototype.replace method. @@search "Symbol.search" A regular expression method that returns the index within a string that matches the regular expression. Called by the String.prototype.search method. @@species "Symbol.species" A function valued property that is the constructor function that is used to create derived objects. @@split "Symbol.split" A regular expression method that splits a string at the indices that match the regular expression. Called by the String.prototype.split method. @@toPrimitive "Symbol.toPrimitive" A method that converts an object to a corresponding primitive value. Called by the ToPrimitive abstract operation. @@toStringTag "Symbol.toStringTag" A String valued property that is used in the creation of the default string description of an object. Accessed by the built-in method Object.prototype.toString. @@unscopables "Symbol.unscopables" An object valued property whose own property names are property names that are excluded from the with environment bindings of the associated object. In them, JSC supports the following 2 symbols. So at this time, exposing them. @@iterator @@unscopables