[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

test/mjsunit/function-bind.js

Index: test/mjsunit/function-bind.js
diff --git a/test/mjsunit/function-bind.js b/test/mjsunit/function-bind.js
index 9c1e1cb0d6f9e1d691f6fe3233730af102b61e72..826986943b9b0341e40cab7d824a212eb4f5afd2 100644
--- a/test/mjsunit/function-bind.js
+++ b/test/mjsunit/function-bind.js
@@ -40,24 +40,29 @@ 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};
@@ -77,6 +82,7 @@ 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.