[Sensors] Implement sensor data polling

third_party/WebKit/Source/modules/sensor/Sensor.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/Sensor.h"
 
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom-blink.h"
 #include "modules/sensor/SensorErrorEvent.h"
@@ skipping 161 matching lines @@
     if (!result)
         reportError();
 
     DCHECK(m_sensorProxy);
     m_sensorProxy->removeObserver(this);
 }
 
 void Sensor::pageVisibilityChanged()
 {
     updatePollingStatus();
+
+    if (!m_sensorProxy || !m_sensorProxy->isInitialized())
+        return;
+
+    if (page()->visibilityState() != PageVisibilityStateVisible) {
+        m_sensorProxy->suspend();
+    } else {
+        m_sensorProxy->resume();
+    }
 }
 
 void Sensor::startListening()
 {
     DCHECK(m_sensorProxy);
     updateState(Sensor::SensorState::ACTIVATING);
     if (!m_sensorReading)
         m_sensorReading = createSensorReading(m_sensorProxy);
 
     m_sensorProxy->addObserver(this);
@@ skipping 62 matching lines @@
 
     if (m_state != Sensor::SensorState::ACTIVE
         || page()->visibilityState() != PageVisibilityStateVisible) {
         m_polling->stopPolling();
     } else {
         m_polling->startPolling();
     }
 }
 
 } // namespace blink