[debugger] implement legacy debug event listeners via debug delegate.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 07b967f2b8cf3bf37e093d1e3724b142d50663ad..ad11dcd2044839b1909a06593d0c91607c17ee6f 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -8896,11 +8896,15 @@ bool Debug::SetDebugEventListener(Isolate* isolate, EventCallback that,
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   ENTER_V8(i_isolate);
   i::HandleScope scope(i_isolate);
-  i::Handle<i::Object> foreign = i_isolate->factory()->undefined_value();
-  if (that != NULL) {
-    foreign = i_isolate->factory()->NewForeign(FUNCTION_ADDR(that));
+  if (that == nullptr) {
+    i_isolate->debug()->SetDebugDelegate(nullptr, false);
+  } else {
+    i::Handle<i::Object> i_data = i_isolate->factory()->undefined_value();
+    if (!data.IsEmpty()) i_data = Utils::OpenHandle(*data);
+    i::NativeDebugDelegate* delegate =
+        new i::NativeDebugDelegate(i_isolate, that, i_data);
+    i_isolate->debug()->SetDebugDelegate(delegate, true);
   }
-  i_isolate->debug()->SetEventListener(foreign, Utils::OpenHandle(*data, true));
   return true;
 }
 
@@ -9353,7 +9357,7 @@ void debug::SetDebugDelegate(Isolate* v8_isolate,
                              debug::DebugDelegate* delegate) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(v8_isolate);
   ENTER_V8(isolate);
-  isolate->debug()->SetDebugDelegate(delegate);
+  isolate->debug()->SetDebugDelegate(delegate, false);
 }
 
 void debug::ResetBlackboxedStateCache(Isolate* v8_isolate,