[runtime] Fix effect of setting .prototype on generator functions.

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 69507124940d5953130b107383d3ad19ae67e5c2..f14a0610217367f74ce07c40414f76a39a162a22 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -182,6 +182,7 @@ enum BindingFlags {
     generator_function_function)                                               \
   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \
   V(INITIAL_ARRAY_PROTOTYPE_INDEX, JSObject, initial_array_prototype)          \
+  V(INITIAL_GENERATOR_PROTOTYPE_INDEX, JSObject, initial_generator_prototype)  \
   V(INITIAL_OBJECT_PROTOTYPE_INDEX, JSObject, initial_object_prototype)        \
   V(INT16_ARRAY_FUN_INDEX, JSFunction, int16_array_fun)                        \
   V(INT16X8_FUNCTION_INDEX, JSFunction, int16x8_function)                      \