Some related work, notably Indify String Concat (JDK-8085796) needs the access to raw String shape. JavaLangAccess is normally used in these cases, but it only has the char[] version now, which invokes the private constructor that shares "chars" array:

      public String newStringUnsafe(char[] chars) {
           return new String(chars, true);
      }

That String(char[],boolean) constructor is copying now, defeating the purpose of JavaLangAccess::newStringUnsafe. Therefore, we need to drill a few new holes in JavaLangAccess to aid these cases, admitting the new String shape.