Add infrastructure to keep track of references to prototypes.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 96e044596d29a67bc71aa4c746a44b0c2180f1ac..7f6eb69fdfd24849feb2c21c72d5015c45a606df 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -762,6 +762,8 @@ class Isolate {
   bool MayIndexedAccess(Handle<JSObject> receiver,
                         uint32_t index,
                         v8::AccessType type);
+  bool IsInternallyUsedPropertyName(Handle<Object> name);
+  bool IsInternallyUsedPropertyName(Object* name);
 
   void SetFailedAccessCheckCallback(v8::FailedAccessCheckCallback callback);
   void ReportFailedAccessCheck(Handle<JSObject> receiver, v8::AccessType type);