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 8da67d270091d294ff4b6343781f9e90b18ed6cc..07750effb3574b74c2cfbc9f5196d08dd7c32316 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -114,10 +114,6 @@ 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)                             \