Reland of [sensors] Ambient light sensor implementation for ChromeOS and Linux.

device/generic_sensor/platform_sensor_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_LINUX_H_
+#define DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_LINUX_H_
+
+#include "device/generic_sensor/platform_sensor.h"
+
+namespace base {
+class RepeatingTimer;
+class SingleThreadTaskRunner;
+class Thread;
+}
+
+namespace device {
+
+class SensorReader;
+struct SensorDataLinux;
+
+class PlatformSensorLinux : public PlatformSensor {
+ public:
+  PlatformSensorLinux(
+      mojom::SensorType type,
+      mojo::ScopedSharedBufferMapping mapping,
+      PlatformSensorProvider* provider,
+      const SensorDataLinux& data,
+      std::unique_ptr<SensorReader> sensor_reader,
+      scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner);
+
+  // Thread safe.
+  mojom::ReportingMode GetReportingMode() override;
+
+ protected:
+  ~PlatformSensorLinux() override;
+  bool StartSensor(const PlatformSensorConfiguration& configuration) override;
+  void StopSensor() override;
+  bool CheckSensorConfiguration(
+      const PlatformSensorConfiguration& configuration) override;
+  PlatformSensorConfiguration GetDefaultConfiguration() override;
+
+ private:
+  void BeginPoll(const PlatformSensorConfiguration& configuration);
+  void StopPoll();
+
+  // Triggers |sensor_reader_| to read new sensor data.
+  // If new data is read, UpdateSensorReading() is called.
+  void PollForReadingData();
+
+  // Owned timer to be deleted on a polling thread.
+  base::RepeatingTimer* timer_;
+
+  const PlatformSensorConfiguration default_configuration_;
+  const mojom::ReportingMode reporting_mode_;
+
+  // A sensor reader that reads values from sensor files
+  // and stores them to a SensorReading structure.
+  std::unique_ptr<SensorReader> sensor_reader_;
+
+  // A task runner that is used to poll sensor data.
+  scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner_;
+
+  // Stores previously read values that are used to
+  // determine whether the recent values are changed
+  // and IPC can be notified that updates are available.
+  SensorReading old_values_;
+
+  base::WeakPtrFactory<PlatformSensorLinux> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformSensorLinux);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_LINUX_H_