[Extensions Bindings] Request JS execution from messaging bindings

extensions/renderer/api_event_handler.cc

Index: extensions/renderer/api_event_handler.cc
diff --git a/extensions/renderer/api_event_handler.cc b/extensions/renderer/api_event_handler.cc
index fc8c3a1a25119d12c11094715aa147751bf4df16..531d68e7fcb17c57c940cde4c2eda10580339f12 100644
--- a/extensions/renderer/api_event_handler.cc
+++ b/extensions/renderer/api_event_handler.cc
@@ -255,6 +255,22 @@ void APIEventHandler::RegisterArgumentMassager(
   data->massagers[event_name].Reset(context->GetIsolate(), massager);
 }
 
+bool APIEventHandler::HasListenerForEvent(const std::string& event_name,
+                                          v8::Local<v8::Context> context) {
+  APIEventPerContextData* data = GetContextData(context, false);
+  if (!data)
+    return false;
+
+  auto iter = data->emitters.find(event_name);
+  if (iter == data->emitters.end())
+    return false;
+  EventEmitter* emitter = nullptr;
+  gin::Converter<EventEmitter*>::FromV8(
+      context->GetIsolate(), iter->second.Get(context->GetIsolate()), &emitter);
+  CHECK(emitter);
+  return emitter->GetNumListeners() > 0;

[lazyboy, 2017/06/05 18:18:32]

Given that we only care about EventEmitter::HasListeners from non-test code
outside of EventEmitter, consider making HasListeners public in EventEmitter and
make GetNumListeners->GetNumListenersForTesting.

[Devlin, 2017/06/09 20:18:01]

Good thought.  Since this patch is already a bit large and that's somewhat
tangential, I've added a TODO for now.

[lazyboy, 2017/06/10 00:09:05]

Acknowledged.

+}
+
 void APIEventHandler::InvalidateContext(v8::Local<v8::Context> context) {
   gin::PerContextData* per_context_data = gin::PerContextData::From(context);
   DCHECK(per_context_data);