[Sensors] Align sensor reading attribute implementation with the specification

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) {}
+SensorReading::SensorReading(const device::SensorReading& data)
+    : m_data(data) {}
 
 SensorReading::~SensorReading() = default;
 
-DEFINE_TRACE(SensorReading) {
-  visitor->trace(m_sensorProxy);
-}
-
 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) {
-    // In cases when SensorReading derived classes are constructed from JS
-    // side, e.g. to create syntetic SensorReadingEvent for testing
-    // purposes, |m_sensorProxy| will be null and SensorReading.timeStamp
-    // would return current DOMHighResTimeStamp, while reading value should
-    // be provided by derived classes.
-    return performance->now();
-  }
-
-  return performance->monotonicTimeToDOMHighResTimeStamp(
-      m_sensorProxy->reading().timestamp);
+  return performance->monotonicTimeToDOMHighResTimeStamp(data().timestamp);
 }
 
 }  // namespace blink