[sensors] [mac] Implement ambient light sensor for macOS

device/generic_sensor/polling_platform_sensor.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_POLLING_PLATFORM_SENSOR_H_
+#define DEVICE_GENERIC_SENSOR_POLLING_PLATFORM_SENSOR_H_
+
+#include "base/timer/timer.h"
+#include "device/generic_sensor/platform_sensor.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace device {
+
+class PollingPlatformSensor : public PlatformSensor {
+ public:
+  PollingPlatformSensor(
+      mojom::SensorType type,
+      mojo::ScopedSharedBufferMapping mapping,
+      PlatformSensorProvider* provider,
+      scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner);
+
+  virtual void UpdateReading() = 0;
+
+ protected:
+  ~PollingPlatformSensor() override;
+  bool StartSensor(const PlatformSensorConfiguration& configuration) override;
+  void StopSensor() override;
+  scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+  base::RepeatingTimer timer_;
+
+ private:
+  void BeginPoll(const PlatformSensorConfiguration& configuration);
+  void StopPoll();
+
+  DISALLOW_COPY_AND_ASSIGN(PollingPlatformSensor);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_POLLING_PLATFORM_SENSOR_H_