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

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 9512 matching lines @@
   DECL_ACCESSORS(handler, Object)
   // [target]: The target property.
   DECL_ACCESSORS(target, Object)
   // [hash]: The hash code property (undefined if not initialized yet).
   DECL_ACCESSORS(hash, Object)
 
   inline bool has_handler();
 
   DECLARE_CAST(JSProxy)
 
+  static bool IsRevoked(Handle<JSProxy> proxy);
+
   // ES6 9.5.1
   static MaybeHandle<Object> GetPrototype(Handle<JSProxy> receiver);
 
+  // ES6 9.5.3
+  MUST_USE_RESULT static Maybe<bool> IsExtensible(Handle<JSProxy> proxy);
+
+  // ES6 9.5.4 (when passed DONT_THROW)
+  MUST_USE_RESULT static Maybe<bool> PreventExtensions(
+      Handle<JSProxy> proxy, ShouldThrow should_throw);
+
   // ES6 9.5.5
   static bool GetOwnPropertyDescriptor(LookupIterator* it,
                                        PropertyDescriptor* desc);
 
   // ES6 9.5.6
   static bool DefineOwnProperty(Isolate* isolate, Handle<JSProxy> object,
                                 Handle<Object> key, PropertyDescriptor* desc,
                                 ShouldThrow should_throw);
 
   MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithHandler(
@@ skipping 32 matching lines @@
 
   typedef FixedBodyDescriptor<kTargetOffset, kSize, kSize> BodyDescriptor;
 
   MUST_USE_RESULT Object* GetIdentityHash();
 
   static Handle<Smi> GetOrCreateIdentityHash(Handle<JSProxy> proxy);
 
  private:
   friend class JSReceiver;
 
+  MUST_USE_RESULT static MaybeHandle<Object> GetTrap(Handle<JSProxy> proxy,
+                                                     Handle<String> trap);
+
   // Invoke a trap by name. If the trap does not exist on this's handler,
   // but derived_trap is non-NULL, invoke that instead.  May cause GC.
   MUST_USE_RESULT static MaybeHandle<Object> CallTrap(
       Handle<JSProxy> proxy, const char* name, Handle<Object> derived_trap,
       int argc, Handle<Object> args[]);
 
   MUST_USE_RESULT static Maybe<bool> HasPropertyWithHandler(
       Handle<JSProxy> proxy, Handle<Name> name);
 
   MUST_USE_RESULT static MaybeHandle<Object> DeletePropertyWithHandler(
@@ skipping 1125 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_