Introduce LanguageMode, drop StrictMode.

src/token.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_TOKEN_H_
 #define V8_TOKEN_H_
 
 #include "src/base/logging.h"
 #include "src/globals.h"
 
@@ skipping 175 matching lines @@
   static const char* Name(Value tok) {
     DCHECK(tok < NUM_TOKENS);  // tok is unsigned
     return name_[tok];
   }
 
   // Predicates
   static bool IsKeyword(Value tok) {
     return token_type[tok] == 'K';
   }
 
-  static bool IsIdentifier(Value tok, StrictMode strict_mode,
+  static bool IsIdentifier(Value tok, LanguageMode language_mode,
                            bool is_generator) {
     switch (tok) {
       case IDENTIFIER:
         return true;
       case FUTURE_STRICT_RESERVED_WORD:
       case LET:
       case STATIC:
-        return strict_mode == SLOPPY;
+        return is_sloppy(language_mode);
       case YIELD:
-        return !is_generator && strict_mode == SLOPPY;
+        return !is_generator && is_sloppy(language_mode);
       default:
         return false;
     }
     UNREACHABLE();
     return false;
   }
 
   static bool IsAssignmentOp(Value tok) {
     return INIT_VAR <= tok && tok <= ASSIGN_MOD;
   }
@@ skipping 95 matching lines @@
  private:
   static const char* const name_[NUM_TOKENS];
   static const char* const string_[NUM_TOKENS];
   static const int8_t precedence_[NUM_TOKENS];
   static const char token_type[NUM_TOKENS];
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_TOKEN_H_