Remove unused code, AstValueFactory::ConcatStrings.

src/ast/ast-value-factory.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 343 matching lines @@
   const AstRawString* GetOneByteString(const char* string) {
     return GetOneByteString(Vector<const uint8_t>(
         reinterpret_cast<const uint8_t*>(string), StrLength(string)));
   }
   const AstRawString* GetTwoByteString(Vector<const uint16_t> literal) {
     return GetTwoByteStringInternal(literal);
   }
   const AstRawString* GetString(Handle<String> literal);
   const AstConsString* NewConsString(const AstString* left,
                                      const AstString* right);
-  const AstRawString* ConcatStrings(const AstRawString* left,
-                                    const AstRawString* right);
 
   void Internalize(Isolate* isolate);
 
 #define F(name, str)                                                    \
   const AstRawString* name##_string() {                                 \
     if (name##_string_ == NULL) {                                       \
       const char* data = str;                                           \
       name##_string_ = GetOneByteString(                                \
           Vector<const uint8_t>(reinterpret_cast<const uint8_t*>(data), \
                                 static_cast<int>(strlen(data))));       \
@@ skipping 64 matching lines @@
   OTHER_CONSTANTS(F)
 #undef F
 };
 }  // namespace internal
 }  // namespace v8
 
 #undef STRING_CONSTANTS
 #undef OTHER_CONSTANTS
 
 #endif  // V8_AST_AST_VALUE_FACTORY_H_