[proxies] Implement [[PreventExtensions]] and [[IsExtensible]].

src/runtime/runtime-object.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 "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug/debug.h"
 #include "src/isolate-inl.h"
@@ skipping 278 matching lines @@
   // 4. Return FromPropertyDescriptor(desc).
   if (!found) return isolate->heap()->undefined_value();
   return *desc.ToObject(isolate);
 }
 
 
 RUNTIME_FUNCTION(Runtime_PreventExtensions) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(JSReceiver, obj, 0);
-  if (JSReceiver::PreventExtensions(obj, Object::THROW_ON_ERROR).IsNothing())
-    return isolate->heap()->exception();
+  MAYBE_RETURN(JSReceiver::PreventExtensions(obj, Object::THROW_ON_ERROR),
+               isolate->heap()->exception());
   return *obj;
 }
 
 
 RUNTIME_FUNCTION(Runtime_IsExtensible) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
-  CONVERT_ARG_HANDLE_CHECKED(JSObject, obj, 0);
-  return isolate->heap()->ToBoolean(JSObject::IsExtensible(obj));
+  CONVERT_ARG_HANDLE_CHECKED(JSReceiver, obj, 0);
+  Maybe<bool> result = JSReceiver::IsExtensible(obj);
+  MAYBE_RETURN(result, isolate->heap()->exception());
+  return isolate->heap()->ToBoolean(result.FromJust());
 }
 
 
 RUNTIME_FUNCTION(Runtime_OptimizeObjectForAddingMultipleProperties) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(JSObject, object, 0);
   CONVERT_SMI_ARG_CHECKED(properties, 1);
   // Conservative upper limit to prevent fuzz tests from going OOM.
   RUNTIME_ASSERT(properties <= 100000);
@@ skipping 1265 matching lines @@
 
 RUNTIME_FUNCTION(Runtime_ObjectDefineProperties) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 2);
   CONVERT_ARG_HANDLE_CHECKED(Object, o, 0);
   CONVERT_ARG_HANDLE_CHECKED(Object, properties, 1);
   return JSReceiver::DefineProperties(isolate, o, properties);
 }
 }  // namespace internal
 }  // namespace v8