Simplify line editor choice in d8.

src/d8.h

 // 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 100 matching lines @@
  private:
   static int Hash(const char* name);
   static bool Match(void* key1, void* key2);
   i::HashMap hash_map_;
 };
 #endif  // V8_SHARED
 
 
 class LineEditor {
  public:
-  enum Type { DUMB = 0, READLINE = 1 };
-  LineEditor(Type type, const char* name);
-  virtual ~LineEditor() { }
-
-  virtual Handle<String> Prompt(const char* prompt) = 0;
-  virtual bool Open() { return true; }
-  virtual bool Close() { return true; }
-  virtual void AddHistory(const char* str) { }
-
-  const char* name() { return name_; }
-  static LineEditor* Get();
+  explicit LineEditor(Isolate* isolate) : isolate_(isolate) { Open(); }
+  ~LineEditor();
+  void Open();
+  const char* name();
+  void AddHistory(const char* str);
+  Handle<String> Prompt(const char* prompt);
  private:
-  Type type_;
-  const char* name_;
-  LineEditor* next_;
-  static LineEditor* first_;
+  Isolate* isolate_;
 };
 
 
 class SourceGroup {
  public:
   SourceGroup() :
 #ifndef V8_SHARED
       next_semaphore_(v8::internal::OS::CreateSemaphore(0)),
       done_semaphore_(v8::internal::OS::CreateSemaphore(0)),
       thread_(NULL),
@@ skipping 260 matching lines @@
   static void ExternalArrayWeakCallback(Isolate* isolate,
                                         Persistent<Value> object,
                                         void* data);
 };
 
 
 }  // namespace v8
 
 
 #endif  // V8_D8_H_