[debugger api] remove legacy JSON debug protocol.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 2ef82dcb73bc184c5adeb20247de0d3ac9a45077..d784673d7f87a4eafccb29dda438a39f8671ed84 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -8895,24 +8895,11 @@ bool Debug::CheckDebugBreak(Isolate* isolate) {
   return internal_isolate->stack_guard()->CheckDebugBreak();
 }
 
-
 void Debug::SetMessageHandler(Isolate* isolate,
-                              v8::Debug::MessageHandler handler) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  ENTER_V8(i_isolate);
-  i_isolate->debug()->SetMessageHandler(handler);
-}
-
-
-void Debug::SendCommand(Isolate* isolate,
-                        const uint16_t* command,
-                        int length,
-                        ClientData* client_data) {
-  i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
-  internal_isolate->debug()->EnqueueCommandMessage(
-      i::Vector<const uint16_t>(command, length), client_data);
-}
+                              v8::Debug::MessageHandler handler) {}
 
+void Debug::SendCommand(Isolate* isolate, const uint16_t* command, int length,
+                        ClientData* client_data) {}
 
 MaybeLocal<Value> Debug::Call(Local<Context> context,
                               v8::Local<v8::Function> fun,
@@ -8953,10 +8940,7 @@ MaybeLocal<Value> Debug::GetMirror(Local<Context> context,
   RETURN_ESCAPED(result);
 }
 
-void Debug::ProcessDebugMessages(Isolate* isolate) {
-  reinterpret_cast<i::Isolate*>(isolate)->debug()->ProcessDebugMessages(true);
-}
-
+void Debug::ProcessDebugMessages(Isolate* isolate) {}
 
 Local<Context> Debug::GetDebugContext(Isolate* isolate) {
   return debug::GetDebugContext(isolate);