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

third_party/WebKit/Source/modules/sensor/SensorUpdateNotificationStrategy.cpp

-// 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.
-
-#include "modules/sensor/SensorUpdateNotificationStrategy.h"
-
-#include "device/generic_sensor/public/interfaces/sensor.mojom-blink.h"
-#include "platform/Timer.h"
-#include "wtf/CurrentTime.h"
-
-namespace blink {
-
-// Polls the buffer on signal from platform but not more frequently
-// than the given 'pollingPeriod'.
-class SensorUpdateNotificationStrategyImpl
-    : public SensorUpdateNotificationStrategy {
- public:
-  SensorUpdateNotificationStrategyImpl(double frequency,
-                                       std::unique_ptr<Function<void()>> func)
-      : m_pollingPeriod(1 / frequency),
-        m_func(std::move(func)),
-        m_timer(this, &SensorUpdateNotificationStrategyImpl::onTimer),
-        m_lastPollingTimestamp(0.0) {
-    DCHECK_GT(frequency, 0.0);
-    DCHECK(m_func);
-  }
-
- private:
-  // SensorUpdateNotificationStrategy overrides.
-  void onSensorReadingChanged() override;
-  void cancelPendingNotifications() override;
-
-  void onTimer(TimerBase*);
-  void notifyUpdate();
-
-  double m_pollingPeriod;
-  std::unique_ptr<Function<void()>> m_func;
-  Timer<SensorUpdateNotificationStrategyImpl> m_timer;
-  double m_lastPollingTimestamp;
-};
-
-void SensorUpdateNotificationStrategyImpl::onSensorReadingChanged() {
-  if (m_timer.isActive())
-    return;  // Skipping changes if update notification was already sheduled.
-
-  double elapsedTime =
-      WTF::monotonicallyIncreasingTime() - m_lastPollingTimestamp;
-
-  double waitingTime = m_pollingPeriod - elapsedTime;
-  const double minInterval =
-      1 / device::mojom::blink::SensorConfiguration::kMaxAllowedFrequency;
-
-  // Negative or zero 'waitingTime' means that polling period has elapsed.
-  // We also avoid scheduling if the elapsed time is slightly behind the
-  // polling period.
-  if (waitingTime < minInterval) {
-    notifyUpdate();
-  } else {
-    m_timer.startOneShot(waitingTime, BLINK_FROM_HERE);
-  }
-}
-
-void SensorUpdateNotificationStrategyImpl::cancelPendingNotifications() {
-  m_timer.stop();
-}
-
-void SensorUpdateNotificationStrategyImpl::notifyUpdate() {
-  m_lastPollingTimestamp = WTF::monotonicallyIncreasingTime();
-  (*m_func)();
-}
-
-void SensorUpdateNotificationStrategyImpl::onTimer(TimerBase*) {
-  notifyUpdate();
-}
-
-// static
-std::unique_ptr<SensorUpdateNotificationStrategy>
-SensorUpdateNotificationStrategy::create(
-    double pollingPeriod,
-    std::unique_ptr<Function<void()>> func) {
-  return std::unique_ptr<SensorUpdateNotificationStrategy>(
-      new SensorUpdateNotificationStrategyImpl(pollingPeriod, std::move(func)));
-}
-
-}  // namespace blink