[Sensors] Align sensor reading attribute implementation with the specification

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

 // 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.
 
 #ifndef SensorProxy_h
 #define SensorProxy_h
 
 #include "core/dom/ExceptionCode.h"
 #include "device/generic_sensor/public/cpp/sensor_reading.h"
 #include "device/generic_sensor/public/interfaces/sensor.mojom-blink.h"
 #include "device/generic_sensor/public/interfaces/sensor_provider.mojom-blink.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "platform/Supplementable.h"
 #include "platform/heap/Handle.h"
 
 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).
 class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
                           public device::mojom::blink::SensorClient {
   USING_PRE_FINALIZER(SensorProxy, dispose);
   WTF_MAKE_NONCOPYABLE(SensorProxy);
 
  public:
   class Observer : public GarbageCollectedMixin {
@@ skipping 25 matching lines @@
                         std::unique_ptr<Function<void(bool)>>);
   void removeConfiguration(device::mojom::blink::SensorConfigurationPtr,
                            std::unique_ptr<Function<void(bool)>>);
 
   void suspend();
   void resume();
 
   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;
   void SensorReadingChanged() override;
 
   // Generic handler for a fatal error.
   // String parameters are intentionally copied.
   void handleSensorError(ExceptionCode = UnknownError,
                          String sanitizedMessage = String(),
                          String unsanitizedMessage = String());
 
   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;
   Member<SensorProviderProxy> m_provider;
   using ObserversSet = HeapHashSet<WeakMember<Observer>>;
   ObserversSet m_observers;
 
   device::mojom::blink::SensorPtr m_sensor;
   device::mojom::blink::SensorConfigurationPtr m_defaultConfig;
   mojo::Binding<device::mojom::blink::SensorClient> m_clientBinding;
 
   enum State { Uninitialized, Initializing, Initialized };
   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) ==
           device::mojom::blink::SensorInitParams::kReadBufferSizeForTests,
       "Check reading buffer size for tests");
 };
 
 }  // namespace blink
 
 #endif  // SensorProxy_h