Fulfill some code serializer related TODOs.

src/code-stubs-hydrogen.cc

Index: src/code-stubs-hydrogen.cc
diff --git a/src/code-stubs-hydrogen.cc b/src/code-stubs-hydrogen.cc
index 70dabb594b14ad0e3e0c2d160ee3158ebaadc92a..32eba7ab84541259347bf36617735320fcc4f925 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -271,8 +271,6 @@ static Handle<Code> DoGenerateCode(Stub* stub) {
   }
   CodeStubGraphBuilder<Stub> builder(isolate, stub);
   LChunk* chunk = OptimizeGraph(builder.CreateGraph());
-  // TODO(yangguo) remove this once the code serializer handles code stubs.
-  if (FLAG_serialize_toplevel) chunk->info()->PrepareForSerializing();
   Handle<Code> code = chunk->Codegen();
   if (FLAG_profile_hydrogen_code_stub_compilation) {
     OFStream os(stdout);