[Sensors] Implement sensor data polling

third_party/WebKit/Source/modules/sensor/SensorPollingStrategy.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 SensorPollingStrategy_h
 #define SensorPollingStrategy_h
 
 #include "device/generic_sensor/public/interfaces/sensor_provider.mojom-blink.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Functional.h"
 
 namespace blink {
 
 // This class provides different polling behaviour depending on
 // the given 'ReportingMode':
 // - for 'CONTINUOUS' mode the polling function is invoked periodically
 //   with the given frequency (on timer event).
 // - for 'ONCHANGE' mode the polling function is invoked only after client
 //   calls 'onSensorReadingChanged()' however considering the given frequency:
 //   guaranteed not to be called more often than expected.
 class SensorPollingStrategy {
 public:
     static std::unique_ptr<SensorPollingStrategy> create(double frequency, std::unique_ptr<Function<void()>> pollFunc, device::mojom::blink::ReportingMode);
 
     virtual void onSensorReadingChanged() {}
     virtual void startPolling() = 0;
     virtual void stopPolling() = 0;
 
     virtual ~SensorPollingStrategy() {}
+
+protected:
+    SensorPollingStrategy(double frequency, std::unique_ptr<Function<void()>>);
+    double m_frequency;
+    std::unique_ptr<Function<void()>> m_pollFunc;
 };
 
 } // namespace blink
 
 #endif // SensorPollingStrategy_h