[Sensors] Align sensor reading updates and 'onchange' notification with rAF.

third_party/WebKit/Source/modules/sensor/SensorReadingUpdater.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 SensorReadingUpdater_h
+#define SensorReadingUpdater_h
+
+#include "device/generic_sensor/public/interfaces/sensor_provider.mojom-blink.h"
+#include "platform/heap/Handle.h"
+
+namespace blink {
+
+class SensorProxy;
+
+// This class encapsulates sensor reading update notification logic.
+class SensorReadingUpdater : public GarbageCollected<SensorProxy> {
+ public:
+  static SensorReadingUpdater* create(SensorProxy*,
+                                      device::mojom::blink::ReportingMode);
+
+  virtual void start();
+
+  DECLARE_VIRTUAL_TRACE();
+
+ protected:
+  explicit SensorReadingUpdater(SensorProxy*);
+  void enqueueAnimationFrameTask();
+  virtual void onAnimationFrameInternal() = 0;
+
+  Member<SensorProxy> m_sensorProxy;
+  bool m_hasPendingAnimationFrameTask;
+
+ private:
+  void onAnimationFrame();
+};
+
+}  // namespace blink
+
+#endif  // SensorReadingUpdater_h