Do not leak private property names to proxy traps and interceptors.

src/messages.h

 // Copyright 2006-2008 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.
 
 // The infrastructure used for (localized) message reporting in V8.
 //
 // Note: there's a big unresolved issue about ownership of the data
 // structures used by this framework.
 
 #ifndef V8_MESSAGES_H_
@@ skipping 239 matching lines @@
   T(ProxyNonObject,                                                            \
     "Cannot create proxy with a non-object as target or handler")              \
   T(ProxyOwnKeysMissing,                                                       \
     "'ownKeys' on proxy: trap result did not include '%'")                     \
   T(ProxyOwnKeysNonExtensible,                                                 \
     "'ownKeys' on proxy: trap returned extra keys but proxy target is "        \
     "non-extensible")                                                          \
   T(ProxyPreventExtensionsExtensible,                                          \
     "'preventExtensions' on proxy: trap returned truish but the proxy target " \
     "is extensible")                                                           \
+  T(ProxyPrivate, "Cannot not pass private property name to proxy trap")       \

[rossberg, 2016/01/11 16:01:42]

Too many negations, dude.

   T(ProxyRevoked, "Cannot perform '%' on a proxy that has been revoked")       \
   T(ProxySetFrozenData,                                                        \
     "'set' on proxy: trap returned truish for property '%' which exists in "   \
     "the proxy target as a non-configurable and non-writable data property "   \
     "with a different value")                                                  \
   T(ProxySetFrozenAccessor,                                                    \
     "'set' on proxy: trap returned truish for property '%' which exists in "   \
     "the proxy target as a non-configurable and non-writable accessor "        \
     "property without a setter")                                               \
   T(ProxySetPrototypeOfNonExtensible,                                          \
@@ skipping 277 matching lines @@
   static Handle<String> GetMessage(Isolate* isolate, Handle<Object> data);
   static base::SmartArrayPointer<char> GetLocalizedMessage(Isolate* isolate,
                                                            Handle<Object> data);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_MESSAGES_H_