Revert of Move //device/generic_sensor to be part of the internal implementation of the Device Service.

device/generic_sensor/platform_sensor_reader_linux.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 DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_READER_LINUX_H_
+#define DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_READER_LINUX_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "device/generic_sensor/generic_sensor_export.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace device {
+
+class PlatformSensorConfiguration;
+class PlatformSensorLinux;
+struct SensorInfoLinux;
+
+// A generic reader class that can be implemented with two different strategies:
+// polling and on trigger. All methods are not thread-safe and must be called
+// on a polling thread that allows I/O.
+class SensorReader {
+ public:
+  // Creates a new instance of SensorReader. At the moment, only polling
+  // reader is supported.
+  static std::unique_ptr<SensorReader> Create(
+      const SensorInfoLinux* sensor_device,
+      base::WeakPtr<PlatformSensorLinux> sensor,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+
+  virtual ~SensorReader();
+
+  // Starts fetching data based on strategy this reader has chosen.
+  // Only polling strategy is supported at the moment.
+  virtual void StartFetchingData(
+      const PlatformSensorConfiguration& configuration) = 0;
+
+  // Stops fetching data.
+  virtual void StopFetchingData() = 0;
+
+ protected:
+  SensorReader(base::WeakPtr<PlatformSensorLinux> sensor,
+               scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+
+  // Notifies |sensor_| about an error.
+  void NotifyReadError();
+
+  // In builds with DCHECK enabled checks that methods of this
+  // and derived classes are called on a right thread.
+  THREAD_CHECKER(thread_checker_);
+
+  // A sensor that this reader is owned by and notifies about errors and
+  // readings to.
+  base::WeakPtr<PlatformSensorLinux> sensor_;
+
+  // A task runner that is used to report about new readings and errors
+  // to a |sensor_|.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  // Indicates if reading is active.
+  bool is_reading_active_;
+
+  DISALLOW_COPY_AND_ASSIGN(SensorReader);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_READER_LINUX_H_