[strong] Fix inlining issue

src/x64/lithium-x64.h

Index: src/x64/lithium-x64.h
diff --git a/src/x64/lithium-x64.h b/src/x64/lithium-x64.h
index be5941c2a2dd6f1e4d163e532e1201a431f7722a..b7f2ab9b018cf5587c2dfaa4360492a54693d1a9 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -1536,6 +1536,10 @@ class LArithmeticT final : public LTemplateInstruction<1, 3, 0> {
   void CompileToNative(LCodeGen* generator) override;
   const char* Mnemonic() const override;
 
+  DECLARE_HYDROGEN_ACCESSOR(BinaryOperation)
+
+  LanguageMode language_mode() { return hydrogen()->language_mode(); }
+
  private:
   Token::Value op_;
 };