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

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 3243636775cef146e6edd103933ced25ff4c15ad..c18d0543d0cd4fde62696e7a18b5c26cf6c05d0b 100644
--- a/third_party/WebKit/Source/modules/sensor/SensorProxy.h
+++ b/third_party/WebKit/Source/modules/sensor/SensorProxy.h
@@ -21,6 +21,7 @@ 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).
@@ -38,7 +39,12 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
     // 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,
@@ -83,16 +89,17 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
 
  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;
@@ -116,8 +123,8 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
   void onRemoveConfigurationCompleted(double frequency, bool result);
 
   bool tryReadFromBuffer(device::SensorReading& result);
-  void updatePollingStatus();
-  void onTimerFired(TimerBase*);
+  bool processRAFQueue();
+  void onAnimationFrame(double timestamp);
 
   device::mojom::blink::SensorType m_type;
   device::mojom::blink::ReportingMode m_mode;
@@ -134,13 +141,16 @@ class SensorProxy final : public GarbageCollectedFinalized<SensorProxy>,
   mojo::ScopedSharedBufferHandle m_sharedBufferHandle;
   mojo::ScopedSharedBufferMapping m_sharedBuffer;
   bool m_suspended;
+  Member<Document> m_document;
   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(