[Sensors] Align sensor reading updates and 'onchange' notification with rAF.

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 "core/page/PageVisibilityObserver.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/Timer.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class SensorProviderProxy;
 class SensorReading;
 class SensorReadingFactory;
+class SensorFrameRequestCallback;
 
 // 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,
                           public PageVisibilityObserver {
   USING_GARBAGE_COLLECTED_MIXIN(SensorProxy);
   USING_PRE_FINALIZER(SensorProxy, dispose);
   WTF_MAKE_NONCOPYABLE(SensorProxy);
 
  public:
   class Observer : public GarbageCollectedMixin {
    public:
     // Has valid 'Sensor' binding, {add, remove}Configuration()
     // methods can be called.
     virtual void onSensorInitialized() {}
     // Platfrom sensort reading has changed.
-    virtual void onSensorReadingChanged() {}
+    // |timestamp| Reference timestamp in seconds of the moment when
+    // sensor reading was updated from the buffer.
+    // Note: |timestamp| values are only used to calculate elapsed time
+    // between shared buffer readings. These values *do not* correspond
+    // to sensor reading timestamps which are obtained on platform side.
+    virtual void onSensorReadingChanged(double timestamp) {}
     // An error has occurred.
     virtual void onSensorError(ExceptionCode,
                                const String& sanitizedMessage,
                                const String& unsanitizedMessage) {}
     // Sensor reading change notification is suspended.
     virtual void onSuspended() {}
   };
 
   ~SensorProxy();
 
@@ skipping 24 matching lines @@
   SensorReading* sensorReading() const { return m_reading; }
 
   const device::mojom::blink::SensorConfiguration* defaultConfig() const;
 
   double maximumFrequency() const { return m_maximumFrequency; }
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class SensorProviderProxy;
+  friend class SensorFrameRequestCallback;
   SensorProxy(device::mojom::blink::SensorType,
               SensorProviderProxy*,
-              Page*,
+              Document*,
               std::unique_ptr<SensorReadingFactory>);
-  // Returns true if this instance is using polling timer to
+  // Returns true if this instance is using rAF to
   // periodically fetch reading data from shared buffer.
-  bool usesPollingTimer() const;
+  bool isPollingBuffer() const;
 
   // Updates sensor reading from shared buffer.
-  void updateSensorReading();
+  void updateSensorReading(double timestamp);
 
   // device::mojom::blink::SensorClient overrides.
   void RaiseError() override;
   void SensorReadingChanged() override;
 
   // PageVisibilityObserver overrides.
   void pageVisibilityChanged() override;
 
   // Generic handler for a fatal error.
   // String parameters are intentionally copied.
   void handleSensorError(ExceptionCode = UnknownError,
                          String sanitizedMessage = String(),
                          String unsanitizedMessage = String());
   // mojo call callbacks.
   void onSensorCreated(device::mojom::blink::SensorInitParamsPtr,
                        device::mojom::blink::SensorClientRequest);
   void onAddConfigurationCompleted(
       double frequency,
       std::unique_ptr<Function<void(bool)>> callback,
       bool result);
   void onRemoveConfigurationCompleted(double frequency, bool result);
 
   bool tryReadFromBuffer(device::SensorReading& result);
   void updatePollingStatus();
-  void onTimerFired(TimerBase*);
+  void onAnimationFrame(double timestamp);
 
   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;
   bool m_suspended;
+  WeakMember<Document> m_document;

[haraken, 2016/12/06 02:38:30]

Is there any reason you want to make it a WeakMember? WeakMember looks okay but
we prefer using a normal Member unless we have a reason to make it weak (because
WeakMember adds some overhead).

   Member<SensorReading> m_reading;
   std::unique_ptr<SensorReadingFactory> m_readingFactory;
   double m_maximumFrequency;
 
   // Used for continious reporting mode.
-  Timer<SensorProxy> m_timer;
+  Member<SensorFrameRequestCallback> m_rafCallback;
+  int m_rafCallbackId;
   WTF::Vector<double> m_frequenciesUsed;
+  double m_lastRafTimestamp;
 
   using ReadingBuffer = device::SensorReadingSharedBuffer;
   static_assert(
       sizeof(ReadingBuffer) ==
           device::mojom::blink::SensorInitParams::kReadBufferSizeForTests,
       "Check reading buffer size for tests");
 };
 
 }  // namespace blink
 
 #endif  // SensorProxy_h