Fix d8-readline to use modern Persistent API

src/d8-readline.cc

 // Copyright 2012 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 132 matching lines @@
   rl_attempted_completion_over = true;
   return result;
 }
 
 
 char* ReadLineEditor::CompletionGenerator(const char* text, int state) {
   static unsigned current_index;
   static Persistent<Array> current_completions;
   Isolate* isolate = read_line_editor.isolate_;
   Locker lock(isolate);
-  HandleScope scope;
+  HandleScope scope(isolate);
   Handle<Array> completions;
   if (state == 0) {
     Local<String> full_text = String::New(rl_line_buffer, rl_point);
     completions = Shell::GetCompletions(isolate, String::New(text), full_text);
     current_completions.Reset(isolate, completions);
     current_index = 0;
   } else {
     completions = Local<Array>::New(isolate, current_completions);
   }
   if (current_index < completions->Length()) {
     Handle<Integer> index = Integer::New(current_index);
     Handle<Value> str_obj = completions->Get(index);
     current_index++;
     String::Utf8Value str(str_obj);
     return strdup(*str);
   } else {
-    current_completions.Dispose(isolate);
-    current_completions.Clear();
+    current_completions.Reset();
     return NULL;
   }
 }
 #endif  // V8_SHARED
 
 
 }  // namespace v8