[proxies] Make Object.{freeze,seal} behave correctly for proxies.

src/runtime/runtime-classes.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/runtime/runtime-utils.h"
 
 #include <stdlib.h>
 #include <limits>
 
 #include "src/arguments.h"
@@ skipping 216 matching lines @@
 RUNTIME_FUNCTION(Runtime_FinalizeClassDefinition) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, constructor, 0);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, prototype, 1);
 
   JSObject::MigrateSlowToFast(constructor, 0, "RuntimeToFastProperties");
 
   if (constructor->map()->is_strong()) {
     DCHECK(prototype->map()->is_strong());
-    RETURN_FAILURE_ON_EXCEPTION(isolate, JSObject::Freeze(prototype));
-    Handle<Object> result;
-    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, result,
-                                       JSObject::Freeze(constructor));
-    return *result;
+    MAYBE_RETURN(JSReceiver::SetIntegrityLevel(prototype, FROZEN,
+                                               Object::THROW_ON_ERROR),
+                 isolate->heap()->exception());
+    MAYBE_RETURN(JSReceiver::SetIntegrityLevel(constructor, FROZEN,
+                                               Object::THROW_ON_ERROR),
+                 isolate->heap()->exception());
   }
   return *constructor;
 }
 
 
 RUNTIME_FUNCTION(Runtime_ClassGetSourceCode) {
   HandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
 
@@ skipping 251 matching lines @@
   Handle<Object> result;
   ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
       isolate, result, Execution::New(isolate, super_constructor, new_target,
                                       argument_count, arguments.get()));
 
   return *result;
 }
 
 }  // namespace internal
 }  // namespace v8