Disallow Object.observe calls on access-checked objects

src/messages.h

Index: src/messages.h
diff --git a/src/messages.h b/src/messages.h
index 4ed94780d1b3fd841b45bdfc9ba8aa1553aa8c98..7b78477a86db67859dfb621ff8c91404fefc2ab0 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -160,6 +160,7 @@ class CallSite {
   T(ObserveCallbackFrozen,                                                     \
     "Object.observe cannot deliver to a frozen function object")               \
   T(ObserveGlobalProxy, "% cannot be called on the global proxy object")       \
+  T(ObserveAccessChecked, "% cannot be called on access-checked objects")      \
   T(ObserveInvalidAccept,                                                      \
     "Third argument to Object.observe must be an array of strings.")           \
   T(ObserveNonFunction, "Object.% cannot deliver to non-function")             \