Make function proxies work as constructors.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index ce6b4a3ccf347a65ab27eda9527cdfd3755d62bf..a76f3b6e81fc408721ed5e2777b8891a1aa7dbd1 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -405,11 +405,7 @@ function FILTER_KEY(key) {
 function CALL_NON_FUNCTION() {
   var delegate = %GetFunctionDelegate(this);
   if (!IS_FUNCTION(delegate)) {
-    if (%IsJSFunctionProxy(this)) {
-      delegate = %GetCallTrap(this);
-    } else {
-      throw %MakeTypeError('called_non_callable', [typeof this]);
-    }
+    throw %MakeTypeError('called_non_callable', [typeof this]);
   }
   return delegate.apply(this, arguments);
 }
@@ -418,11 +414,7 @@ function CALL_NON_FUNCTION() {
 function CALL_NON_FUNCTION_AS_CONSTRUCTOR() {
   var delegate = %GetConstructorDelegate(this);
   if (!IS_FUNCTION(delegate)) {
-    if (%IsJSFunctionProxy(this)) {
-      delegate = %GetConstructTrap(this);
-    } else {
-      throw %MakeTypeError('called_non_callable', [typeof this]);
-    }
+    throw %MakeTypeError('called_non_callable', [typeof this]);
   }
   return delegate.apply(this, arguments);
 }
@@ -434,25 +426,16 @@ function CALL_FUNCTION_PROXY() {
   var trap = %GetCallTrap(proxy);
   // TODO(rossberg): hm, shouldn't I be using $Function and friends?
   // But how do I get it in a builtin?
-  return global.Function.prototype.apply.call(
-    trap, this, global.Array.prototype.slice.call(arguments, 0, arity));
+  return Function.prototype.apply.call(
+    trap, this, Array.prototype.slice.call(arguments, 0, arity));
 }
 
 
-function CALL_FUNCTION_PROXY_AS_CONSTRUCTOR(proxy) {
+function CALL_FUNCTION_PROXY_AS_CONSTRUCTOR() {
+  var proxy = this;
   var trap = %GetConstructTrap(proxy);
-  var receiver = void 0;
-  if (!IS_UNDEFINED(trap)) {
-    trap = %GetCallTrap(proxy);
-    var proto = proxy.prototype;
-    if (!IS_SPEC_OBJECT(proto) && proto !== null) {
-      throw MakeTypeError("proto_object_or_null", [proto]);
-    }
-    receiver = new global.Object();
-    receiver.__proto__ = proto;
-  }
-  return global.Function.prototype.apply.call(
-    trap, this, global.Array.prototype.shift.call(arguments));
+  // TODO(rossberg): should be using $Function or a builtin somehow.
+  return Function.prototype.apply.call(trap, this, arguments);
 }