[Sensors] Align sensor reading attribute implementation with the specification

third_party/WebKit/Source/modules/sensor/SensorProxy.h

Index: third_party/WebKit/Source/modules/sensor/SensorProxy.h
diff --git a/third_party/WebKit/Source/modules/sensor/SensorProxy.h b/third_party/WebKit/Source/modules/sensor/SensorProxy.h
index 942b0d7bad0a78bba1934509b17548160c6eb6cc..faf62de4966b148e868f342539482bb56d1af5f9 100644
--- a/third_party/WebKit/Source/modules/sensor/SensorProxy.h
+++ b/third_party/WebKit/Source/modules/sensor/SensorProxy.h
@@ -16,6 +16,8 @@
 namespace blink {
 
 class SensorProviderProxy;
+class SensorReading;
+class SensorReadingFactory;
 
 // This class wraps 'Sensor' mojo interface and used by multiple
 // JS sensor instances of the same type (within a single frame).
@@ -61,20 +63,23 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
   device::mojom::blink::SensorType type() const { return m_type; }
   device::mojom::blink::ReportingMode reportingMode() const { return m_mode; }
 
-  using Reading = device::SensorReading;
-
-  const Reading& reading() const { return m_reading; }
+  // The |SensorReading| instance which is shared between sensor instances
+  // of the same type.
+  // Note: the returned value is reset after updateSensorReading() call.
+  SensorReading* sensorReading() const { return m_reading; }
 
   const device::mojom::blink::SensorConfiguration* defaultConfig() const;
 
-  // Updates internal reading from shared buffer.
-  void updateInternalReading();
+  // Updates sensor reading from shared buffer.
+  void updateSensorReading();
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class SensorProviderProxy;
-  SensorProxy(device::mojom::blink::SensorType, SensorProviderProxy*);
+  SensorProxy(device::mojom::blink::SensorType,
+              SensorProviderProxy*,
+              std::unique_ptr<SensorReadingFactory>);
 
   // device::mojom::blink::SensorClient overrides.
   void RaiseError() override;
@@ -89,7 +94,7 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
   void onSensorCreated(device::mojom::blink::SensorInitParamsPtr,
                        device::mojom::blink::SensorClientRequest);
 
-  bool tryReadFromBuffer();
+  bool tryReadFromBuffer(device::SensorReading& result);
 
   device::mojom::blink::SensorType m_type;
   device::mojom::blink::ReportingMode m_mode;
@@ -105,8 +110,10 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
   State m_state;
   mojo::ScopedSharedBufferHandle m_sharedBufferHandle;
   mojo::ScopedSharedBufferMapping m_sharedBuffer;
-  Reading m_reading;
   bool m_suspended;
+  Member<SensorReading> m_reading;
+  std::unique_ptr<SensorReadingFactory> m_readingFactory;
+
   using ReadingBuffer = device::SensorReadingSharedBuffer;
   static_assert(
       sizeof(ReadingBuffer) ==