[Extensions Bindings] Add Events support

extensions/renderer/event_emitter.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/event_emitter.h"
+
+#include <algorithm>
+
+#include "gin/object_template_builder.h"
+
+namespace extensions {
+
+gin::WrapperInfo EventEmitter::kWrapperInfo = {gin::kEmbedderNativeGin};
+
+EventEmitter::EventEmitter() {}
+
+EventEmitter::~EventEmitter() {}
+
+gin::ObjectTemplateBuilder EventEmitter::GetObjectTemplateBuilder(
+    v8::Isolate* isolate) {
+  return Wrappable<EventEmitter>::GetObjectTemplateBuilder(isolate)
+      .SetMethod("addListener", &EventEmitter::AddListener)
+      .SetMethod("removeListener", &EventEmitter::RemoveListener)
+      .SetMethod("hasListener", &EventEmitter::HasListener)
+      .SetMethod("hasListeners", &EventEmitter::HasListeners);
+}
+
+void EventEmitter::AddListener(gin::Arguments* arguments) {
+  v8::Local<v8::Function> listener;
+  if (!arguments->GetNext(&listener))
+    return;
+
+  if (!HasListener(listener)) {
+    listeners_.push_back(
+        v8::Global<v8::Function>(arguments->isolate(), listener));
+  }
+}
+
+void EventEmitter::RemoveListener(v8::Local<v8::Function> listener) {
+  auto iter = std::find(listeners_.begin(), listeners_.end(), listener);
+  if (iter != listeners_.end())
+    listeners_.erase(iter);
+}
+
+bool EventEmitter::HasListener(v8::Local<v8::Function> listener) {
+  return std::find(listeners_.begin(), listeners_.end(), listener) !=
+         listeners_.end();
+}
+
+bool EventEmitter::HasListeners() {
+  return !listeners_.empty();
+}
+
+}  // namespace extensions