[Sensors] Fix reading updates after page refresh

third_party/WebKit/Source/modules/sensor/SensorReadingUpdater.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/SensorReadingUpdater.h"
 
 #include "core/dom/Document.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom-blink.h"
 #include "modules/sensor/SensorProxy.h"
 #include "wtf/CurrentTime.h"
 
 using device::mojom::blink::ReportingMode;
 
 namespace blink {
 
 SensorReadingUpdater::SensorReadingUpdater(SensorProxy* sensorProxy)
     : m_sensorProxy(sensorProxy), m_hasPendingAnimationFrameTask(false) {}
 
 void SensorReadingUpdater::enqueueAnimationFrameTask() {
   if (m_hasPendingAnimationFrameTask)
     return;
 
   auto callback = WTF::bind(&SensorReadingUpdater::onAnimationFrame,

[shalamov, 2017/01/20 09:25:32]

can be moved inside if (...)

[Mikhail, 2017/01/24 12:00:18]

Done.

                             wrapWeakPersistent(this));
-  m_sensorProxy->document()->enqueueAnimationFrameTask(std::move(callback));
-  m_hasPendingAnimationFrameTask = true;
+  auto document = m_sensorProxy->document();
+  if (document) {
+    document->enqueueAnimationFrameTask(std::move(callback));
+    m_hasPendingAnimationFrameTask = true;
+  }
 }
 
 void SensorReadingUpdater::start() {
   enqueueAnimationFrameTask();
 }
 
+void SensorReadingUpdater::reset() {
+  m_hasPendingAnimationFrameTask = false;

[haraken, 2017/01/19 13:57:28]

Would you help me understand why you need to set it to false here?

Also even if you set it to false, the animation frame task is not yet canceled.
 

[shalamov, 2017/01/20 09:25:33]

haraken@ is right, looks like if task was enqueued, setting to false would not
stop consecutive "enqueue" calls when callback is called, right?

[Mikhail, 2017/01/24 12:00:18]

I thought it as just a "reset" of the internal state of the object, anyway the
latest patch does not contain it :)

+}
+
 void SensorReadingUpdater::onAnimationFrame() {
   m_hasPendingAnimationFrameTask = false;
   onAnimationFrameInternal();
 }
 
 DEFINE_TRACE(SensorReadingUpdater) {
   visitor->trace(m_sensorProxy);
 }
 
 class SensorReadingUpdaterContinuous : public SensorReadingUpdater {
@@ skipping 60 matching lines @@
 
 // static
 SensorReadingUpdater* SensorReadingUpdater::create(SensorProxy* proxy,
                                                    ReportingMode mode) {
   if (mode == ReportingMode::CONTINUOUS)
     return new SensorReadingUpdaterContinuous(proxy);
   return new SensorReadingUpdaterOnChange(proxy);
 }
 
 }  // namespace blink