[Extensions Bindings] Request JS execution from messaging bindings

extensions/renderer/api_event_handler.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extensions/renderer/api_event_handler.h"
 
 #include <algorithm>
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 239 matching lines @@
 
 void APIEventHandler::RegisterArgumentMassager(
     v8::Local<v8::Context> context,
     const std::string& event_name,
     v8::Local<v8::Function> massager) {
   APIEventPerContextData* data = GetContextData(context, true);
   DCHECK(data->massagers.find(event_name) == data->massagers.end());
   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;
+}
+
 void APIEventHandler::InvalidateContext(v8::Local<v8::Context> context) {
   gin::PerContextData* per_context_data = gin::PerContextData::From(context);
   DCHECK(per_context_data);
   APIEventPerContextData* data = static_cast<APIEventPerContextData*>(
       per_context_data->GetUserData(kExtensionAPIEventPerContextKey));
   if (!data)
     return;
 
   v8::Isolate* isolate = context->GetIsolate();
   v8::HandleScope scope(isolate);
@@ skipping 35 matching lines @@
   auto iter = data->emitters.find(event_name);
   DCHECK(iter != data->emitters.end());
   EventEmitter* emitter = nullptr;
   gin::Converter<EventEmitter*>::FromV8(
       context->GetIsolate(), iter->second.Get(context->GetIsolate()), &emitter);
   CHECK(emitter);
   return emitter->GetNumListeners();
 }
 
 }  // namespace extensions