Make function proxies work as constructors.

src/v8natives.js

 // Copyright 2011 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 1027 matching lines @@
 }
 
 
 // Harmony proxies.
 function ProxyFix(obj) {
   var handler = %GetHandler(obj);
   var props = CallTrap0(handler, "fix", void 0);
   if (IS_UNDEFINED(props)) {
     throw MakeTypeError("handler_returned_undefined", [handler, "fix"]);
   }
-
   if (IS_FUNCTION(obj)) {
     var callTrap = %GetCallTrap(obj);
     var constructTrap = %GetConstructTrap(obj);
     var code = DelegateCallAndConstruct(callTrap, constructTrap);
     %Fix(obj);  // becomes a regular function
     %SetCode(obj, code);
+    // TODO(rossberg): What about length and other properties? Not specified.
+    // We just put in some half-reasonable defaults for now.
+    var prototype = new $Object();
+    $Object.defineProperty(prototype, "constructor",
+      {value: obj, writable: true, enumerable: false, configrable: true});
+    $Object.defineProperty(obj, "prototype",
+      {value: prototype, writable: true, enumerable: false, configrable: false})
+    $Object.defineProperty(obj, "length",
+      {value: 0, writable: true, enumerable: false, configrable: false});
   } else {
     %Fix(obj);
   }
   ObjectDefineProperties(obj, props);
 }
 
 
 // ES5 section 15.2.3.8.
 function ObjectSeal(obj) {
   if (!IS_SPEC_OBJECT(obj)) {
@@ skipping 487 matching lines @@
 // ----------------------------------------------------------------------------
 
 function SetupFunction() {
   InstallFunctions($Function.prototype, DONT_ENUM, $Array(
     "bind", FunctionBind,
     "toString", FunctionToString
   ));
 }
 
 SetupFunction();