[sensors] Ambient light sensor bindings implementation

third_party/WebKit/Source/modules/sensor/SensorReading.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/SensorReading.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/timing/DOMWindowPerformance.h"
 #include "core/timing/Performance.h"
 
 namespace blink {
 
 SensorReading::SensorReading(SensorProxy* sensorProxy)
     : m_sensorProxy(sensorProxy)
 {
-    DCHECK(m_sensorProxy);
 }
 
 DEFINE_TRACE(SensorReading)
 {
     visitor->trace(m_sensorProxy);
 }
 
+SensorReading::~SensorReading() = default;
+
+bool SensorReading::isReadingUpdated(const SensorProxy::Reading& previous) const
+{
+    return false;
+}
+
 DOMHighResTimeStamp SensorReading::timeStamp(ScriptState* scriptState) const
 {
     LocalDOMWindow* window = scriptState->domWindow();
     if (!window)
         return 0.0;
 
     Performance* performance = DOMWindowPerformance::performance(*window);
     DCHECK(performance);
 
+    if (!m_sensorProxy)
+        return performance->now();
+
     return performance->monotonicTimeToDOMHighResTimeStamp(m_sensorProxy->reading().timestamp);
 }
 
 } // namespace blink