Add infrastructure to keep track of references to prototypes.

src/isolate.cc

 // 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.
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
 
 #include "src/v8.h"
@@ skipping 784 matching lines @@
 
     if (Context::cast(receiver_context)->security_token() ==
         native_context->security_token())
       return YES;
   }
 
   return UNKNOWN;
 }
 
 
+bool Isolate::IsInternallyUsedPropertyName(Handle<Object> name) {
+  return name.is_identical_to(factory()->hidden_string()) ||
+         name.is_identical_to(factory()->prototype_users_symbol());
+}
+
+
+bool Isolate::IsInternallyUsedPropertyName(Object* name) {
+  return name == heap()->hidden_string() ||
+         name == heap()->prototype_users_symbol();
+}
+
+
 bool Isolate::MayNamedAccess(Handle<JSObject> receiver,
                              Handle<Object> key,
                              v8::AccessType type) {
   DCHECK(receiver->IsJSGlobalProxy() || receiver->IsAccessCheckNeeded());
 
-  // Skip checks for hidden properties access.  Note, we do not
+  // Skip checks for internally used properties. Note, we do not
   // require existence of a context in this case.
-  if (key.is_identical_to(factory()->hidden_string())) return true;
+  if (IsInternallyUsedPropertyName(key)) return true;
 
   // Check for compatibility between the security tokens in the
   // current lexical context and the accessed object.
   DCHECK(context());
 
   MayAccessDecision decision = MayAccessPreCheck(this, receiver, type);
   if (decision != UNKNOWN) return decision == YES;
 
   HandleScope scope(this);
   Handle<Object> data;
@@ skipping 1728 matching lines @@
   if (prev_ && prev_->Intercept(flag)) return true;
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 } }  // namespace v8::internal