Implement Android shared memory data fetcher for Device Motion.

content/browser/device_orientation/data_fetcher_shared_memory.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_DATA_FETCHER_SHARED_MEMORY_H_
+#define CONTENT_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_SHARED_MEMORY_H_
+
+#include "content/browser/device_orientation/device_data.h"
+#include "content/common/device_motion_hardware_buffer.h"
+
+namespace WebKit {
+class WebDeviceMotionData;
+}
+
+namespace content {
+
+class DataFetcherSharedMemory {
+ public:
+  static DataFetcherSharedMemory* instance();
+
+  // Returns true if this fetcher needs explicit calls to fetch the data.
+  virtual bool NeedsPolling();
+
+  // If this fetcher needsPolling() is true, this method will update the

[bulach, 2013/07/09 09:03:29]

nit: s/needs/Needs/ here and below..

[timvolodine, 2013/07/09 18:59:56]

Done.

+  // buffer with the latest device motion data.
+  // This method will do nothing if needsPolling() is false.
+  // Returns true if there was any motion data to update the buffer with.
+  virtual bool FetchDeviceMotionDataIntoBuffer();
+
+  // Returns true if the relevant sensors could be successfully activated.
+  // This method should be called before any calls to
+  // FetchDeviceMotionDataIntoBuffer().
+  virtual bool StartFetchingDeviceMotionData(
+      DeviceMotionHardwareBuffer* buffer);
+
+  // Indicates to the fetcher to stop fetching device data.
+  virtual void StopFetchingDeviceMotionData();
+  virtual ~DataFetcherSharedMemory();

[bulach, 2013/07/09 09:03:29]

since the only way to get one object is via "instance()", the destructor will
never be called, and no callers should try to destroy one, right? in that case,
make this destructor private?

[timvolodine, 2013/07/09 18:59:56]

Done.

+
+ protected:
+  DataFetcherSharedMemory() : device_motion_buffer_(NULL) { }
+

[bulach, 2013/07/09 09:03:29]

nit: private:
(data members and the DISALLOW_* macros can't be protected)

[timvolodine, 2013/07/09 18:59:56]

Done.

+  DeviceMotionHardwareBuffer* device_motion_buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataFetcherSharedMemory);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_DEVICE_ORIENTATION_DATA_FETCHER_SHARED_MEMORY_H_