[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

test/mjsunit/function-bind.js

 // Copyright 2010 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 22 matching lines @@
 // Simple tests.
 function foo(x, y, z) {
   return [this, arguments.length, x];
 }
 
 assertEquals(3, foo.length);
 
 var f = foo.bind(foo);
 assertEquals([foo, 3, 1], f(1, 2, 3));
 assertEquals(3, f.length);
+assertEquals("function () { [native code] }", f.toString());
 
 f = foo.bind(foo, 1);
 assertEquals([foo, 3, 1], f(2, 3));
 assertEquals(2, f.length);
+assertEquals("function () { [native code] }", f.toString());
 
 f = foo.bind(foo, 1, 2);
 assertEquals([foo, 3, 1], f(3));
 assertEquals(1, f.length);
+assertEquals("function () { [native code] }", f.toString());
 
 f = foo.bind(foo, 1, 2, 3);
 assertEquals([foo, 3, 1], f());
 assertEquals(0, f.length);
+assertEquals("function () { [native code] }", f.toString());
 
 // Test that length works correctly even if more than the actual number
 // of arguments are given when binding.
 f = foo.bind(foo, 1, 2, 3, 4, 5, 6, 7, 8, 9);
 assertEquals([foo, 9, 1], f());
 assertEquals(0, f.length);
+assertEquals("function () { [native code] }", f.toString());
 
 // Use a different bound object.
 var obj = {x: 42, y: 43};
 // Values that would normally be in "this" when calling f_bound_this.
 var x = 42;
 var y = 44;
 
 function f_bound_this(z) {
   return z + this.y - this.x;
 }
 
 assertEquals(3, f_bound_this(1))
 f = f_bound_this.bind(obj);
 assertEquals(2, f(1));
 assertEquals(1, f.length);
 
 f = f_bound_this.bind(obj, 2);
 assertEquals(3, f());
 assertEquals(0, f.length);
+assertEquals('[object Function]', Object.prototype.toString.call(f));
 
 // Test chained binds.
 
 // When only giving the thisArg, any number of binds should have
 // the same effect.
 f = foo.bind(foo);
 assertEquals([foo, 3, 1], f(1, 2, 3));
 
 var not_foo = {};
 f = foo.bind(foo).bind(not_foo).bind(not_foo).bind(not_foo);
@@ skipping 221 matching lines @@
   var bound = fun.bind({});
   assertEquals(proto, Object.getPrototypeOf(bound));
 
   var bound2 = fun.bind({});
   assertTrue(%HaveSameMap(new bound, new bound2));
 
   Object.setPrototypeOf(fun, null);
   bound = Function.prototype.bind.call(fun, {});
   assertEquals(null, Object.getPrototypeOf(bound));
 })();