Allow constants to be deleted by reinserting them into the graph as needed.

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 a695161801999b29da4342e3f9b86a92a600c409..a273c1b19a185f8081926a6777477ff9a76420a1 100644
--- a/src/code-stubs-hydrogen.cc
+++ b/src/code-stubs-hydrogen.cc
@@ -150,10 +150,6 @@ bool CodeStubGraphBuilderBase::BuildGraph() {
   next_block->SetJoinId(BailoutId::StubEntry());
   set_current_block(next_block);
 
-  HConstant* undefined_constant =
-      Add<HConstant>(isolate()->factory()->undefined_value());
-  graph()->set_undefined_constant(undefined_constant);
-
   for (int i = 0; i < param_count; ++i) {
     HParameter* param =
         Add<HParameter>(i, HParameter::REGISTER_PARAMETER);