[Extensions Bindings] Add Events support

extensions/renderer/api_event_handler.h

+// 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.
+
+#ifndef EXTENSIONS_RENDERER_API_EVENT_HANDLER_H_
+#define EXTENSIONS_RENDERER_API_EVENT_HANDLER_H_
+
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/supports_user_data.h"
+#include "extensions/renderer/api_binding_types.h"
+#include "v8/include/v8.h"
+
+namespace base {
+class ListValue;
+}
+
+namespace gin {
+class Arguments;
+}
+
+namespace extensions {
+
+// The object to handle API events. This includes vending v8::Objects for the
+// event; handling adding, removing, and querying listeners; and firing events
+// to subscribed listeners. Designed to be used across JS contexts, but on a
+// single thread.
+class APIEventHandler {
+ public:
+  using EventListeners = std::vector<v8::Global<v8::Function>>;
+  using HandlerCallback =
+      base::Callback<void(v8::Local<v8::Object>, gin::Arguments*)>;
+
+  APIEventHandler(const binding::RunJSFunction& call_js);
+  ~APIEventHandler();
+
+  // Returns a new v8::Object for an event with the given |event_name|.
+  v8::Local<v8::Object> CreateEventInstance(const std::string& event_name,
+                                            v8::Local<v8::Context> context);
+
+  // Notifies all listeners of the event with the given |event_name| in the
+  // specified |context|, sending the included |arguments|.
+  void FireEventInContext(const std::string& event_name,
+                          v8::Local<v8::Context> context,
+                          const base::ListValue& arguments);
+
+  // Returns the EventListeners for a given |event_name| and |context|.
+  const EventListeners& GetEventListenersForTesting(
+      const std::string& event_name,
+      v8::Local<v8::Context> context);
+
+ private:
+  struct APIEventPerContextData : public base::SupportsUserData::Data {
+    APIEventPerContextData();
+    ~APIEventPerContextData() override;
+
+    // A map from event name -> event listeners.
+    std::map<std::string, std::unique_ptr<EventListeners>> event_data;
+
+    std::vector<std::unique_ptr<HandlerCallback>> callbacks;
+  };
+
+  void InitializeTemplate(v8::Isolate* isolate, APIEventPerContextData* data);
+
+  // Returns the EventListeners associated with the given |object|.
+  EventListeners* GetListenersForObject(v8::Local<v8::Object> object,
+                                        v8::Local<v8::Context> context);
+
+  // Functions to add, remove, or query event listeners. Forwarded from the
+  // JS entry points.
+  void AddListener(v8::Local<v8::Object> caller, gin::Arguments* arguments);
+  void RemoveListener(v8::Local<v8::Object> caller, gin::Arguments* arguments);
+  void HasListener(v8::Local<v8::Object> caller, gin::Arguments* arguments);
+  void HasListeners(v8::Local<v8::Object> caller, gin::Arguments* arguments);
+
+  // Method to run a given v8::Function. Curried in for testing.
+  binding::RunJSFunction call_js_;
+
+  v8::Global<v8::ObjectTemplate> event_template_;
+
+  base::WeakPtrFactory<APIEventHandler> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(APIEventHandler);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_API_EVENT_HANDLER_H_