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 a998d4dc7197834c558fbc9f74d36829a2a5c376..5a7d2f9b0f8fca10c4564834236ca22be0bea502 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);