Introduce LanguageMode, drop StrictMode.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 2c9f1fb94d264c93044d0386dc097dcdbea7f10b..7843476958a619b32566bc5e7e767efbd7a78a3a 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -571,16 +571,16 @@ class NumberToStringStub FINAL : public HydrogenCodeStub {
 
 class FastNewClosureStub : public HydrogenCodeStub {
  public:
-  FastNewClosureStub(Isolate* isolate, StrictMode strict_mode,
+  FastNewClosureStub(Isolate* isolate, LanguageMode language_mode,
                      FunctionKind kind)
       : HydrogenCodeStub(isolate) {
     DCHECK(IsValidFunctionKind(kind));
-    set_sub_minor_key(StrictModeBits::encode(strict_mode) |
+    set_sub_minor_key(LanguageModeBits::encode(language_mode) |
                       FunctionKindBits::encode(kind));
   }
 
-  StrictMode strict_mode() const {
-    return StrictModeBits::decode(sub_minor_key());
+  LanguageMode language_mode() const {
+    return LanguageModeBits::decode(sub_minor_key());
   }
 
   FunctionKind kind() const {
@@ -592,7 +592,8 @@ class FastNewClosureStub : public HydrogenCodeStub {
   bool is_default_constructor() const { return IsDefaultConstructor(kind()); }
 
  private:
-  class StrictModeBits : public BitField<StrictMode, 0, 1> {};
+  STATIC_ASSERT(LANGUAGE_END == 2);
+  class LanguageModeBits : public BitField<LanguageMode, 0, 1> {};
   class FunctionKindBits : public BitField<FunctionKind, 1, 4> {};
 
   DEFINE_CALL_INTERFACE_DESCRIPTOR(FastNewClosure);