Revert "Handlify concat string and substring."

src/objects.cc

 // Copyright 2013 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 9285 matching lines @@
       if (is_index) is_index = hasher.UpdateIndex(c);
     }
   }
   *utf16_length_out = static_cast<int>(utf16_length);
   // Must set length here so that hash computation is correct.
   hasher.length_ = utf16_length;
   return hasher.GetHashField();
 }
 
 
+MaybeObject* String::SubString(int start, int end, PretenureFlag pretenure) {
+  Heap* heap = GetHeap();
+  if (start == 0 && end == length()) return this;
+  MaybeObject* result = heap->AllocateSubString(this, start, end, pretenure);
+  return result;
+}
+
+
 void String::PrintOn(FILE* file) {
   int length = this->length();
   for (int i = 0; i < length; i++) {
     PrintF(file, "%c", Get(i));
   }
 }
 
 
 static void TrimEnumCache(Heap* heap, Map* map, DescriptorArray* descriptors) {
   int live_enum = map->EnumLength();
@@ skipping 7162 matching lines @@
 #define ERROR_MESSAGES_TEXTS(C, T) T,
   static const char* error_messages_[] = {
       ERROR_MESSAGES_LIST(ERROR_MESSAGES_TEXTS)
   };
 #undef ERROR_MESSAGES_TEXTS
   return error_messages_[reason];
 }
 
 
 } }  // namespace v8::internal