[turbofan] Add proper conversion operators for int32<->int64.

test/compiler-unittests/compiler-unittests.h

Index: test/compiler-unittests/compiler-unittests.h
diff --git a/test/compiler-unittests/compiler-unittests.h b/test/compiler-unittests/compiler-unittests.h
index 82e95794169690b76577437f03e3363ef8bde8ed..03541e73a2be1bb1d8ff5f136b551b16498969ce 100644
--- a/test/compiler-unittests/compiler-unittests.h
+++ b/test/compiler-unittests/compiler-unittests.h
@@ -73,6 +73,11 @@ class CompilerTest : public ::testing::Test {
   Zone zone_;
 };
 
+
+template <typename T>
+class CompilerTestWithParam : public CompilerTest,
+                              public ::testing::WithParamInterface<T> {};
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8