[runtime] Support Proxy setPrototypeOf trap

src/runtime/runtime-object.cc

Index: src/runtime/runtime-object.cc
diff --git a/src/runtime/runtime-object.cc b/src/runtime/runtime-object.cc
index 707b05e57b756ccffc0b9ba422b0f2c0b1fde14a..3547446975cd9e1b81b3ecd7702fd87699edf011 100644
--- a/src/runtime/runtime-object.cc
+++ b/src/runtime/runtime-object.cc
@@ -182,9 +182,15 @@ RUNTIME_FUNCTION(Runtime_SetPrototype) {
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, obj, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, prototype, 1);
-  MAYBE_RETURN(
-      JSReceiver::SetPrototype(obj, prototype, true, Object::THROW_ON_ERROR),
-      isolate->heap()->exception());
+
+  Maybe<bool> status =
+      JSReceiver::SetPrototype(obj, prototype, true, Object::THROW_ON_ERROR);
+  if (status.IsNothing()) return isolate->heap()->exception();
+  if (!status.FromJust()) {

[Camillo Bruni, 2015/11/16 13:32:08]

We should probably throw the error already in JSProxy::SetPrototype in case the
trap return false, thus allowing for a more specific error message.

+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kObjectSetPrototypeFailed, obj,
+                              prototype));
+  }
   return *obj;
 }