Revert of [debugger api] remove legacy JSON debug protocol.

include/v8-debug.h

Index: include/v8-debug.h
diff --git a/include/v8-debug.h b/include/v8-debug.h
index 7100925b3a700e18f4e2eafae41aa530533795ac..777b8aaa3e645a1c6024d46ebab5bbc70754cd1b 100644
--- a/include/v8-debug.h
+++ b/include/v8-debug.h
@@ -24,21 +24,45 @@
 class V8_EXPORT Debug {
  public:
   /**
-   * An event details object passed to the debug event listener.
-   */
-  class EventDetails {
+   * A client object passed to the v8 debugger whose ownership will be taken by
+   * it. v8 is always responsible for deleting the object.
+   */
+  class ClientData {
    public:
-    /**
-     * Event type.
-     */
+    virtual ~ClientData() {}
+  };
+
+
+  /**
+   * A message object passed to the debug message handler.
+   */
+  class Message {
+   public:
+    /**
+     * Check type of message.
+     */
+    virtual bool IsEvent() const = 0;
+    virtual bool IsResponse() const = 0;
     virtual DebugEvent GetEvent() const = 0;
 
     /**
-     * Access to execution state and event data of the debug event. Don't store
-     * these cross callbacks as their content becomes invalid.
+     * Indicate whether this is a response to a continue command which will
+     * start the VM running after this is processed.
+     */
+    virtual bool WillStartRunning() const = 0;
+
+    /**
+     * Access to execution state and event data. Don't store these cross
+     * callbacks as their content becomes invalid. These objects are from the
+     * debugger event that started the debug message loop.
      */
     virtual Local<Object> GetExecutionState() const = 0;
     virtual Local<Object> GetEventData() const = 0;
+
+    /**
+     * Get the debugger protocol JSON.
+     */
+    virtual Local<String> GetJSON() const = 0;
 
     /**
      * Get the context active when the debug event happened. Note this is not
@@ -48,11 +72,56 @@
     virtual Local<Context> GetEventContext() const = 0;
 
     /**
+     * Client data passed with the corresponding request if any. This is the
+     * client_data data value passed into Debug::SendCommand along with the
+     * request that led to the message or NULL if the message is an event. The
+     * debugger takes ownership of the data and will delete it even if there is
+     * no message handler.
+     */
+    virtual ClientData* GetClientData() const = 0;
+
+    virtual Isolate* GetIsolate() const = 0;
+
+    virtual ~Message() {}
+  };
+
+  /**
+   * An event details object passed to the debug event listener.
+   */
+  class EventDetails {
+   public:
+    /**
+     * Event type.
+     */
+    virtual DebugEvent GetEvent() const = 0;
+
+    /**
+     * Access to execution state and event data of the debug event. Don't store
+     * these cross callbacks as their content becomes invalid.
+     */
+    virtual Local<Object> GetExecutionState() const = 0;
+    virtual Local<Object> GetEventData() const = 0;
+
+    /**
+     * Get the context active when the debug event happened. Note this is not
+     * the current active context as the JavaScript part of the debugger is
+     * running in its own context which is entered at this point.
+     */
+    virtual Local<Context> GetEventContext() const = 0;
+
+    /**
      * Client data passed with the corresponding callback when it was
      * registered.
      */
     virtual Local<Value> GetCallbackData() const = 0;
 
+    /**
+     * Client data passed to DebugBreakForCommand function. The
+     * debugger takes ownership of the data and will delete it even if
+     * there is no message handler.
+     */
+    virtual ClientData* GetClientData() const = 0;
+
     virtual Isolate* GetIsolate() const = 0;
 
     virtual ~EventDetails() {}
@@ -63,10 +132,25 @@
    *
    * \param event_details object providing information about the debug event
    *
-   * A EventCallback does not take possession of the event data,
+   * A EventCallback2 does not take possession of the event data,
    * and must not rely on the data persisting after the handler returns.
    */
   typedef void (*EventCallback)(const EventDetails& event_details);
+
+  /**
+   * Debug message callback function.
+   *
+   * \param message the debug message handler message object
+   *
+   * A MessageHandler does not take possession of the message data,
+   * and must not rely on the data persisting after the handler returns.
+   */
+  typedef void (*MessageHandler)(const Message& message);
+
+  /**
+   * Callback function for the host to ensure debug messages are processed.
+   */
+  typedef void (*DebugMessageDispatchHandler)();
 
   static bool SetDebugEventListener(Isolate* isolate, EventCallback that,
                                     Local<Value> data = Local<Value>());
@@ -82,6 +166,16 @@
   // Check if a debugger break is scheduled in the given isolate.
   V8_DEPRECATED("No longer supported",
                 static bool CheckDebugBreak(Isolate* isolate));
+
+  // Message based interface. The message protocol is JSON.
+  V8_DEPRECATED("No longer supported",
+                static void SetMessageHandler(Isolate* isolate,
+                                              MessageHandler handler));
+
+  V8_DEPRECATED("No longer supported",
+                static void SendCommand(Isolate* isolate,
+                                        const uint16_t* command, int length,
+                                        ClientData* client_data = NULL));
 
   /**
    * Run a JavaScript function in the debugger.
@@ -114,6 +208,40 @@
                                                    v8::Local<v8::Value> obj));
 
   /**
+   * Makes V8 process all pending debug messages.
+   *
+   * From V8 point of view all debug messages come asynchronously (e.g. from
+   * remote debugger) but they all must be handled synchronously: V8 cannot
+   * do 2 things at one time so normal script execution must be interrupted
+   * for a while.
+   *
+   * Generally when message arrives V8 may be in one of 3 states:
+   * 1. V8 is running script; V8 will automatically interrupt and process all
+   * pending messages;
+   * 2. V8 is suspended on debug breakpoint; in this state V8 is dedicated
+   * to reading and processing debug messages;
+   * 3. V8 is not running at all or has called some long-working C++ function;
+   * by default it means that processing of all debug messages will be deferred
+   * until V8 gets control again; however, embedding application may improve
+   * this by manually calling this method.
+   *
+   * Technically this method in many senses is equivalent to executing empty
+   * script:
+   * 1. It does nothing except for processing all pending debug messages.
+   * 2. It should be invoked with the same precautions and from the same context
+   * as V8 script would be invoked from, because:
+   *   a. with "evaluate" command it can do whatever normal script can do,
+   *   including all native calls;
+   *   b. no other thread should call V8 while this method is running
+   *   (v8::Locker may be used here).
+   *
+   * "Evaluate" debug command behavior currently is not specified in scope
+   * of this method.
+   */
+  V8_DEPRECATED("No longer supported",
+                static void ProcessDebugMessages(Isolate* isolate));
+
+  /**
    * Debugger is running in its own context which is entered while debugger
    * messages are being dispatched. This is an explicit getter for this
    * debugger context. Note that the content of the debugger context is subject