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

src/log.h

Index: src/log.h
diff --git a/src/log.h b/src/log.h
index 78312059343fc239a6e6e27959c881804ddf81ca..b7a5fc6bd3cd961c57a039e1aaf2bb2cc15a95cb 100644
--- a/src/log.h
+++ b/src/log.h
@@ -135,6 +135,12 @@
   // Emits an event that an undefined property was read from an
   // object.
   void SuspectReadEvent(Name* name, Object* obj);
+
+  // Emits an event when a message is put on or read from a debugging queue.
+  // DebugTag lets us put a call-site specific label on the event.
+  void DebugTag(const char* call_site_tag);
+  void DebugEvent(const char* event_type, Vector<uint16_t> parameter);
+
 
   // ==== Events logged by --log-api. ====
   void ApiSecurityCheck();