[sensors] [win] Implement ambient light sensor for Windows platform

device/generic_sensor/platform_sensor_reader_win.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_WIN_H_
+#define DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_READER_WIN_H_
+
+#include <SensorsApi.h>
+
+#include "base/win/scoped_comptr.h"
+#include "device/generic_sensor/public/interfaces/sensor.mojom.h"
+
+namespace device {
+
+class PlatformSensorConfiguration;
+struct ReaderInitParams;
+struct SensorReading;
+
+// Generic class that uses ISensor interface to fetch sensor data. Used
+// by PlatformSensorWin and delivers notifications via Client interface.
+// Instances of this class must be created and destucted on sensor thread.

[Mikhail, 2016/10/26 13:35:31]

nit: destucted on same thread. ?

[Reilly Grant (use Gerrit), 2016/10/27 00:59:20]

s/destucted/destructed/

[shalamov, 2016/10/27 13:51:07]

Done.

[shalamov, 2016/10/27 13:51:08]

Done.

+class PlatformSensorReaderWin {
+ public:
+  // Client interface that can be used to receive notifications about sensor
+  // error or data change events.
+  class Client {
+   public:
+    virtual void OnReadingUpdated(const SensorReading& reading) = 0;
+    virtual void OnSensorError() = 0;
+
+   protected:
+    virtual ~Client() {}
+  };
+
+  static std::unique_ptr<PlatformSensorReaderWin> Create(
+      mojom::SensorType type,
+      base::win::ScopedComPtr<ISensorManager> sensor_manager);
+
+  // Following methods are thread safe.
+  void SetClient(Client* client);
+  unsigned long GetMinimalReportingIntervalMs() const;
+  mojom::ReportingMode GetReportingMode() const;
+  bool StartSensor(const PlatformSensorConfiguration& configuration);
+  void StopSensor();
+
+  // Must be destructed on sensor thread.
+  ~PlatformSensorReaderWin();
+
+ private:
+  PlatformSensorReaderWin(base::win::ScopedComPtr<ISensor> sensor,
+                          std::unique_ptr<ReaderInitParams> params);
+
+  static base::win::ScopedComPtr<ISensor> GetSensorForType(
+      REFSENSOR_TYPE_ID sensor_type,
+      base::win::ScopedComPtr<ISensorManager> sensor_manager);
+
+  bool SetReportingInterval(const PlatformSensorConfiguration& configuration);
+  HRESULT SensorReadingChanged(ISensorDataReport& report,
+                               SensorReading& reading) const;
+  void SensorError();
+
+ private:
+  friend class EventListener;

[Reilly Grant (use Gerrit), 2016/10/27 00:59:20]

nit: spaces between friends, fields and the DISALLOW_COPY_AND_ASSIGN macro.

[shalamov, 2016/10/27 13:51:08]

Done.

+  base::Lock lock_;

[Reilly Grant (use Gerrit), 2016/10/27 00:59:19]

Document why these fields (and which ones) must be protected by a lock. I'm
assuming it's because of MTA?

[shalamov, 2016/10/27 13:51:08]

Yes. MTA allows to use COM interfaces from different threads, yet,
synchronization must be provided for concurrent access.

+  bool sensor_active_;
+  Client* client_;
+  const std::unique_ptr<ReaderInitParams> init_params_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  base::win::ScopedComPtr<ISensor> sensor_;
+  scoped_refptr<EventListener> event_listener_;
+  DISALLOW_COPY_AND_ASSIGN(PlatformSensorReaderWin);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_GENERIC_SENSOR_PLATFORM_SENSOR_READER_WIN_H_