Remove more dead code after Object.observe removal

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 55739c5bc49142f0a24cee82101c6b39aeafff5b..611b5cd523f8c5dd54708df84c90b7c1f6d480e0 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -111,10 +111,6 @@ enum BindingFlags {
   V(MESSAGE_GET_COLUMN_NUMBER_INDEX, JSFunction, message_get_column_number)   \
   V(MESSAGE_GET_LINE_NUMBER_INDEX, JSFunction, message_get_line_number)       \
   V(MESSAGE_GET_SOURCE_LINE_INDEX, JSFunction, message_get_source_line)       \
-  V(NATIVE_OBJECT_GET_NOTIFIER_INDEX, JSFunction, native_object_get_notifier) \
-  V(NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE, JSFunction,                        \
-    native_object_notifier_perform_change)                                    \
-  V(NATIVE_OBJECT_OBSERVE_INDEX, JSFunction, native_object_observe)           \
   V(NO_SIDE_EFFECTS_TO_STRING_FUN_INDEX, JSFunction,                          \
     no_side_effects_to_string_fun)                                            \
   V(OBJECT_VALUE_OF, JSFunction, object_value_of)                             \