[Parser] Introduce AstStringConstants to share constants across AstValueFactory

src/ast/ast-value-factory.cc

 // 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 203 matching lines @@
       break;
     case THE_HOLE:
       set_value(isolate->factory()->the_hole_value());
       break;
     case UNDEFINED:
       set_value(isolate->factory()->undefined_value());
       break;
   }
 }
 
-
 AstRawString* AstValueFactory::GetOneByteStringInternal(
     Vector<const uint8_t> literal) {
   if (literal.length() == 1 && IsInRange(literal[0], 'a', 'z')) {
     int key = literal[0] - 'a';
     if (one_character_strings_[key] == nullptr) {
       uint32_t hash = StringHasher::HashSequentialString<uint8_t>(
           literal.start(), literal.length(), hash_seed_);
       one_character_strings_[key] = GetString(hash, true, literal);
     }
     return one_character_strings_[key];
@@ skipping 163 matching lines @@
                                   length) == 0;
     } else {
       return CompareCharsUnsigned(reinterpret_cast<const uint16_t*>(l),
                                   reinterpret_cast<const uint16_t*>(r),
                                   length) == 0;
     }
   }
 }
 }  // namespace internal
 }  // namespace v8