Revert of There are only 2 language modes, not 3

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index 3468963e23e929f609430873b6f1e19c33ec15c0..3480b866baaffbd46fefa4270a7595e48cbacd88 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -488,8 +488,8 @@
   // Scope-specific information computed during parsing.
   //
   // The language mode of this scope.
-  STATIC_ASSERT(LANGUAGE_END == 2);
-  LanguageMode language_mode_ : 1;
+  STATIC_ASSERT(LANGUAGE_END == 3);
+  LanguageMode language_mode_ : 2;
   // This scope is inside a 'with' of some outer scope.
   bool scope_inside_with_ : 1;
   // This scope or a nested catch scope or with scope contain an 'eval' call. At