There are only 2 language modes, not 3

src/parsing/parser.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_PARSING_PARSER_H_
 #define V8_PARSING_PARSER_H_
 
 #include "src/allocation.h"
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
@@ skipping 157 matching lines @@
   void set_isolate(Isolate* isolate) { isolate_ = isolate; }
   void set_shared_info(Handle<SharedFunctionInfo> shared) { shared_ = shared; }
   void set_context(Handle<Context> context) { context_ = context; }
   void set_script(Handle<Script> script) { script_ = script; }
   //--------------------------------------------------------------------------
 
   LanguageMode language_mode() const {
     return construct_language_mode(is_strict_mode());
   }
   void set_language_mode(LanguageMode language_mode) {
-    STATIC_ASSERT(LANGUAGE_END == 3);
+    STATIC_ASSERT(LANGUAGE_END == 2);
     set_strict_mode(is_strict(language_mode));
   }
 
   void ReopenHandlesInNewHandleScope() {
     shared_ = Handle<SharedFunctionInfo>(*shared_);
     script_ = Handle<Script>(*script_);
     context_ = Handle<Context>(*context_);
   }
 
 #ifdef DEBUG
@@ skipping 1188 matching lines @@
 
 DoExpression* ParserTraits::ParseDoExpression(bool* ok) {
   return parser_->ParseDoExpression(ok);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_H_