[turbofan] Make sure Operator is really immutable.

test/cctest/compiler/test-js-context-specialization.cc

Index: test/cctest/compiler/test-js-context-specialization.cc
diff --git a/test/cctest/compiler/test-js-context-specialization.cc b/test/cctest/compiler/test-js-context-specialization.cc
index 740d9f3d497350c78e14bf83388b4a85df7d41a7..fd573c16f22a3987571162aec4e615227580fad0 100644
--- a/test/cctest/compiler/test-js-context-specialization.cc
+++ b/test/cctest/compiler/test-js-context-specialization.cc
@@ -95,8 +95,7 @@ TEST(ReduceJSLoadContext) {
     CHECK_EQ(IrOpcode::kHeapConstant, new_context_input->opcode());
     ValueMatcher<Handle<Context> > match(new_context_input);
     CHECK_EQ(*native, *match.Value());
-    ContextAccess access = static_cast<Operator1<ContextAccess>*>(
-                               r.replacement()->op())->parameter();
+    ContextAccess access = OpParameter<ContextAccess>(r.replacement());
     CHECK_EQ(Context::GLOBAL_EVAL_FUN_INDEX, access.index());
     CHECK_EQ(0, access.depth());
     CHECK_EQ(false, access.immutable());
@@ -176,8 +175,7 @@ TEST(ReduceJSStoreContext) {
     CHECK_EQ(IrOpcode::kHeapConstant, new_context_input->opcode());
     ValueMatcher<Handle<Context> > match(new_context_input);
     CHECK_EQ(*native, *match.Value());
-    ContextAccess access = static_cast<Operator1<ContextAccess>*>(
-                               r.replacement()->op())->parameter();
+    ContextAccess access = OpParameter<ContextAccess>(r.replacement());
     CHECK_EQ(Context::GLOBAL_EVAL_FUN_INDEX, access.index());
     CHECK_EQ(0, access.depth());
     CHECK_EQ(false, access.immutable());