[Sensors] Align sensor reading attribute implementation with the specification

third_party/WebKit/Source/modules/sensor/SensorProviderProxy.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/SensorProviderProxy.h"
 
 #include "modules/sensor/SensorProxy.h"
+#include "modules/sensor/SensorReading.h"
 #include "platform/mojo/MojoHelper.h"
 #include "public/platform/InterfaceProvider.h"
 #include "public/platform/Platform.h"
 
 namespace blink {
 
 // SensorProviderProxy
 SensorProviderProxy::SensorProviderProxy(LocalFrame* frame) {
   frame->interfaceProvider()->getInterface(mojo::GetProxy(&m_sensorProvider));
   m_sensorProvider.set_connection_error_handler(convertToBaseCallback(
@@ skipping 16 matching lines @@
   return result;
 }
 
 SensorProviderProxy::~SensorProviderProxy() {}
 
 DEFINE_TRACE(SensorProviderProxy) {
   visitor->trace(m_sensors);
   Supplement<LocalFrame>::trace(visitor);
 }
 
-SensorProxy* SensorProviderProxy::getOrCreateSensor(
+SensorProxy* SensorProviderProxy::createSensor(
+    device::mojom::blink::SensorType type,
+    std::unique_ptr<SensorReadingFactory> readingFactory) {
+  DCHECK(!getSensor(type));
+
+  SensorProxy* sensor = new SensorProxy(type, this, std::move(readingFactory));
+  m_sensors.add(sensor);
+
+  return sensor;
+}
+
+SensorProxy* SensorProviderProxy::getSensor(
     device::mojom::blink::SensorType type) {
   for (SensorProxy* sensor : m_sensors) {
     // TODO(Mikhail) : Hash sensors by type for efficiency.
     if (sensor->type() == type)
       return sensor;
   }
 
-  SensorProxy* sensor = new SensorProxy(type, this);
-  m_sensors.add(sensor);
-
-  return sensor;
+  return nullptr;
 }
 
 void SensorProviderProxy::onSensorProviderConnectionError() {
   if (!Platform::current()) {
     // TODO(rockot): Clean this up once renderer shutdown sequence is fixed.
     return;
   }
 
   m_sensorProvider.reset();
   for (SensorProxy* sensor : m_sensors)
     sensor->handleSensorError();
 }
 
 }  // namespace blink