Implement the content/renderer and content/browser part of the Device Motion API.

content/browser/device_orientation/device_motion_service.h

+// Copyright (c) 2013 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 CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_MOTION_SERVICE_H_
+#define CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_MOTION_SERVICE_H_
+
+#include "base/basictypes.h"
+#include "base/callback_forward.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/singleton.h"
+#include "base/shared_memory.h"
+#include "base/threading/thread_checker.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+class DataFetcherSharedMemory;
+class DeviceMotionProvider;
+class RenderProcessHost;
+
+// Owns the DeviceMotionProvider (the background polling thread) and keeps
+// track of the number of consumers currently using the data (and pausing
+// the provider when not in use).
+class CONTENT_EXPORT DeviceMotionService {
+ public:
+  // Returns the DeviceMotionService singleton.
+  static DeviceMotionService* GetInstance();
+
+  // 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.
+  //
+  // Must be called on the I/O thread.
+  void AddConsumer();
+
+  // Removes a consumer. Should be matched with an AddConsumer call.
+  //
+  // Must be called on the I/O thread.
+  void RemoveConsumer();
+
+  // Returns the shared memory handle of the device motion data duplicated
+  // into the given process.
+  base::SharedMemoryHandle GetSharedMemoryHandleForProcess(
+      base::ProcessHandle handle);
+
+  // Stop/join with the background thread in DeviceMotionProvider |provider_|.
+  void Shutdown();
+
+ private:
+  friend struct DefaultSingletonTraits<DeviceMotionService>;
+
+  DeviceMotionService();
+  virtual ~DeviceMotionService();
+
+  int num_readers_;
+  bool is_shutdown_;
+  scoped_ptr<DeviceMotionProvider> provider_;
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeviceMotionService);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_DEVICE_MOTION_SERVICE_H_