[sensors] Fix component build warnings for windows platform

device/generic_sensor/public/cpp/sensor_reading.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_PUBLIC_CPP_SENSOR_READING_H_
 #define DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_READING_H_
 
 #include "device/base/synchronization/one_writer_seqlock.h"
 #include "device/generic_sensor/generic_sensor_export.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom.h"
@@ skipping 32 matching lines @@
 struct DEVICE_GENERIC_SENSOR_EXPORT SensorReading {
   SensorReading();
   ~SensorReading();
   SensorReading(const SensorReading& other);
   SensorReadingField<double> timestamp;
   SensorReadingField<double> values[3];
 };
 
 // This structure represents sensor reading buffer: sensor reading and seqlock
 // for synchronization.
-struct SensorReadingSharedBuffer {
+struct DEVICE_GENERIC_SENSOR_EXPORT SensorReadingSharedBuffer {
   SensorReadingSharedBuffer();
   ~SensorReadingSharedBuffer();
   SensorReadingField<OneWriterSeqLock> seqlock;
   SensorReading reading;
 
   // Gets the shared reading buffer offset for the given sensor type.
   static uint64_t GetOffset(mojom::SensorType type);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_GENERIC_SENSOR_PUBLIC_CPP_SENSOR_READING_H_