[proxies] Make Object.{isFrozen,isSealed} behave correctly for proxies.

src/objects.h

 // Copyright 2012 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.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/allocation.h"
@@ skipping 1853 matching lines @@
   static bool GetOwnPropertyDescriptor(LookupIterator* it,
                                        PropertyDescriptor* desc);
 
   typedef PropertyAttributes IntegrityLevel;
 
   // ES6 7.3.14 (when passed DONT_THROW)
   // 'level' must be SEALED or FROZEN.
   MUST_USE_RESULT static Maybe<bool> SetIntegrityLevel(
       Handle<JSReceiver> object, IntegrityLevel lvl, ShouldThrow should_throw);
 
+  // ES6 7.3.15
+  // 'level' must be SEALED or FROZEN.
+  MUST_USE_RESULT static Maybe<bool> TestIntegrityLevel(
+      Handle<JSReceiver> object, IntegrityLevel lvl);
+
   // ES6 [[PreventExtensions]] (when passed DONT_THROW)
   MUST_USE_RESULT static Maybe<bool> PreventExtensions(
       Handle<JSReceiver> object, ShouldThrow should_throw);
 
   MUST_USE_RESULT static Maybe<bool> IsExtensible(Handle<JSReceiver> object);
 
   // Tests for the fast common case for property enumeration.
   bool IsSimpleEnum();
 
   // Returns the class name ([[Class]] property in the specification).
@@ skipping 8793 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_