Replace boolean indications of strict mode by an enum value.

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 c9474068e3e676924006d7e7f56b9a289863b1a3..20a69373c1241cb9b797acac4c57e8c1ac2b2494 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -1572,7 +1572,8 @@ class LStoreNamedGeneric: public LTemplateInstruction<0, 2, 0> {
   LOperand* object() { return inputs_[0]; }
   LOperand* value() { return inputs_[1]; }
   Handle<Object> name() const { return hydrogen()->name(); }
-  bool strict_mode() { return hydrogen()->strict_mode(); }
+  StrictModeFlag strict_mode_flag() { return hydrogen()->strict_mode_flag(); }
+  bool strict_mode() { return strict_mode_flag() == kStrictMode; }
 };