Introduce LanguageMode, drop StrictMode.

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 2025117d82252d44074e7a30dc75cf217985d87d..ec54c7d5836689948d0e47f9014a4c4a1bed24ff 100644
--- a/src/x64/lithium-x64.h
+++ b/src/x64/lithium-x64.h
@@ -2212,7 +2212,7 @@ class LStoreNamedGeneric FINAL : public LTemplateInstruction<0, 3, 0> {
   void PrintDataTo(StringStream* stream) OVERRIDE;
 
   Handle<Object> name() const { return hydrogen()->name(); }
-  StrictMode strict_mode() { return hydrogen()->strict_mode(); }
+  LanguageMode language_mode() { return hydrogen()->language_mode(); }
 };
 
 
@@ -2267,7 +2267,7 @@ class LStoreKeyedGeneric FINAL : public LTemplateInstruction<0, 4, 0> {
 
   void PrintDataTo(StringStream* stream) OVERRIDE;
 
-  StrictMode strict_mode() { return hydrogen()->strict_mode(); }
+  LanguageMode language_mode() { return hydrogen()->language_mode(); }
 };