To fully support hydrogen code stubs which accept a variable number of arguments,

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 9c8225ea459d449fa6809a13253425671e3af984..f7fcfeb97a40924bf182b666bee0b93c49ca781c 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -270,6 +270,13 @@ struct CodeStubInterfaceDescriptor {
   int extra_expression_stack_count_;
   Register* register_params_;
   Address deoptimization_handler_;
+
+  int environment_length() const {
+    if (stack_parameter_count_ != NULL) {
+      return register_param_count_ + 1;
+    }
+    return register_param_count_;
+  }
 };