Replace boolean indications of strict mode by an enum value.

src/x64/lithium-codegen-x64.h

Index: src/x64/lithium-codegen-x64.h
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index a521c148ab50098b000d050f1d5d1b6c909d17f8..f3cb667973ce58c486e85c1ff752f09f34e666a8 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -126,8 +126,8 @@ class LCodeGen BASE_EMBEDDED {
   bool is_done() const { return status_ == DONE; }
   bool is_aborted() const { return status_ == ABORTED; }
 
-  int strict_mode_flag() const {
-    return info()->is_strict_mode() ? kStrictMode : kNonStrictMode;
+  StrictModeFlag strict_mode_flag() const {
+    return info()->strict_mode_flag();
   }
 
   LChunk* chunk() const { return chunk_; }