Revert of [runtime] Replace global object link with native context link in all contexts.

src/snapshot/serialize.cc

Index: src/snapshot/serialize.cc
diff --git a/src/snapshot/serialize.cc b/src/snapshot/serialize.cc
index b88bb59d61cc61982bcd0db9091a9c08fbab3a9e..8da750a22217942410fa596a58d5b796c41e2c5f 100644
--- a/src/snapshot/serialize.cc
+++ b/src/snapshot/serialize.cc
@@ -1853,8 +1853,6 @@
   ObjectSerializer serializer(this, obj, sink_, how_to_code, where_to_point);
   serializer.Serialize();
 
-  // TODO(yangguo): We probably only need ScriptContext here for post-
-  // processing in Genesis::HookUpGlobalThisBinding.
   if (obj->IsContext() &&
       Context::cast(obj)->global_object() == global_object_) {
     // Context refers to the current global object. This reference will