Add GamepadService, owns 1 gamepad bg thread

content/browser/gamepad/gamepad_service.h

+// Copyright (c) 2011 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.
+
+// Owns the GamepadProvider (the background polling thread) and keeps track of
+// the number of renderers currently using the data (and pausing the provider
+// when not in use).
+
+#ifndef CONTENT_BROWSER_GAMEPAD_GAMEPAD_SERVICE_H
+#define CONTENT_BROWSER_GAMEPAD_GAMEPAD_SERVICE_H
+
+#include "base/basictypes.h"
+#include "base/memory/singleton.h"
+#include "base/shared_memory.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+namespace content {
+
+class GamepadDataFetcher;
+class GamepadProvider;
+class RenderProcessHost;
+
+class GamepadService : public NotificationObserver {
+ public:
+  // Returns the GamepadService singleton.
+  static GamepadService* GetInstance();
+
+  // Called on IO thread from a renderer host. Increments the number of users
+  // of the provider. The Provider is running when there's > 0 users, and is
+  // paused when the count drops to 0. There is no stop, the gamepad service
+  // registers with the RPH to be notified when the associated renderer closes
+  // (or crashes).
+  void Start(GamepadDataFetcher* fetcher,
+             RenderProcessHost* associated_rph);
+
+  base::SharedMemoryHandle GetSharedMemoryHandle(base::ProcessHandle handle);
+
+ private:
+  friend struct DefaultSingletonTraits<GamepadService>;
+  friend class base::RefCountedThreadSafe<GamepadService>;
+  GamepadService();
+  virtual ~GamepadService();
+
+  // Called when a renderer that Start'd us is closed/crashes.
+  void Stop();
+
+  // Run on UI thread to receive notifications of renderer closes.
+  void RegisterForCloseNotification(RenderProcessHost* rph);
+
+  // NotificationObserver overrides:
+  virtual void Observe(int type,
+                       const NotificationSource& source,
+                       const NotificationDetails& details) OVERRIDE;
+
+  // A registrar for listening notifications. Used to listen for when an
+  // associated renderer has gone away (possibly crashed). We don't trust
+  // the renderers to send a stop message because of the possibility of
+  // crashing.
+  NotificationRegistrar registrar_;
+
+  int num_readers_;
+  scoped_refptr<GamepadProvider> provider_;
+
+  DISALLOW_COPY_AND_ASSIGN(GamepadService);
+};
+
+} // namespace content
+
+#endif // CONTENT_BROWSER_GAMEPAD_GAMEPAD_SERVICE_H