Add the basic code skeleton for system info event router

chrome/browser/extensions/system_info_event_router.h

+// Copyright (c) 2012 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 CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_EVENT_ROUTER_H_
+#define CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_EVENT_ROUTER_H_
+
+#include "base/file_path.h"
+#include "base/memory/singleton.h"
+#include "base/values.h"
+
+namespace extensions {
+
+// Event router for systemInfo API. It is a singleton instance shared by
+// multiple profiles.
+// TODO(hongbo): It should derive from SystemMonitor::DevicesChangedObserver.
+// Since the system_monitor will be refactored along with media_gallery, once
+// http://crbug.com/145400 is fixed, we need to update SystemInfoEventRouter
+// accordingly.
+class SystemInfoEventRouter {
+ public:
+  static SystemInfoEventRouter* GetInstance();
+
+  // Add/remove event listener for the |event_name| event from |profile|.
+  void AddEventListener(const std::string& event_name);
+  void RemoveEventListener(const std::string& event_name);
+
+  // Return true if the |event_name| is an event from systemInfo namespace.
+  static bool IsSystemInfoEvent(const std::string& event_name);
+
+  // TODO(hongbo): The following methods should be likely overriden from
+  // SystemMonitor::DevicesChangedObserver once the http://crbug.com/145400
+  // is fixed.
+  void OnStorageAvailableCapacityChanged(const std::string& id,
+                                         int64 available_capacity);
+  void OnRemovableStorageAttached(const std::string& id,
+                                  const string16& name,
+                                  const FilePath::StringType& location);
+  void OnRemovableStorageDetached(const std::string& id);
+
+ private:
+  friend struct DefaultSingletonTraits<SystemInfoEventRouter>;
+  // The map of event name which has been watching already to the count it has
+  // been watched.
+  typedef std::map<std::string, int> EventWatchingMap;

[Mihai Parparita -not on Chrome, 2012/09/01 00:20:53]

Nit: I think this can just be a std::multiset<std::string>.

[Hongbo Min, 2012/09/02 02:47:12]

Done.

+
+  SystemInfoEventRouter();
+  virtual ~SystemInfoEventRouter();
+
+  // Called on the UI thread to dispatch the systemInfo event to all extension
+  // processes cross multiple profiles.
+  void DispatchEvent(const std::string& event_name,
+      scoped_ptr<base::ListValue> args);
+
+  // Used to record the number of being watched for the event.
+  EventWatchingMap event_watching_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemInfoEventRouter);
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_SYSTEM_INFO_EVENT_ROUTER_H_