[Sensors] Decouple sensor readings update from 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 "platform/wtf/Vector.h"
 
 namespace blink {
 
 class SensorProviderProxy;
 class SensorReading;
-class SensorReadingUpdater;
 
 // 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 sensor reading has changed.
-    virtual void OnSensorReadingChanged() {}
-    // Observer should send 'onchange' event if needed.
-    // The 'notifySensorChanged' calls are in sync with rAF.
-    // Currently, we decide whether to send 'onchange' event based on the
-    // time elapsed from the previous notification.
-    // TODO: Reconsider this after https://github.com/w3c/sensors/issues/152
-    // is resolved.
+    // Observer should update its cached reading and send 'onchange'
+    // event if needed.
     // |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 NotifySensorChanged(double timestamp) {}
+    virtual void OnSensorReadingChanged(double timestamp) {}
     // An error has occurred.
     virtual void OnSensorError(ExceptionCode,
                                const String& sanitized_message,
                                const String& unsanitized_message) {}
   };
 
   ~SensorProxy();
 
   void Dispose();
 
   void AddObserver(Observer*);
   void RemoveObserver(Observer*);
 
   void Initialize();
 
   bool IsInitializing() const { return state_ == kInitializing; }
   bool IsInitialized() const { return state_ == kInitialized; }
 
-  // Is watching new reading data (initialized, not suspended and has
-  // configurations added).
-  bool IsActive() const;
-
   void AddConfiguration(device::mojom::blink::SensorConfigurationPtr,
                         std::unique_ptr<Function<void(bool)>>);
 
   void RemoveConfiguration(device::mojom::blink::SensorConfigurationPtr);
 
   void Suspend();
   void Resume();
 
-  device::mojom::blink::SensorType GetType() const { return type_; }
-  device::mojom::blink::ReportingMode GetReportingMode() const { return mode_; }
+  device::mojom::blink::SensorType type() const { return type_; }
 
   // Note: the returned value is reset after updateSensorReading() call.
-  const device::SensorReading& Reading() const { return reading_; }
+  const device::SensorReading& reading() const { return reading_; }
 
   const device::mojom::blink::SensorConfiguration* DefaultConfig() const;
 
   const std::pair<double, double>& FrequencyLimits() const {
     return frequency_limits_;
   }
 
-  Document* GetDocument() const;
-  const WTF::Vector<double>& FrequenciesUsed() const {
-    return frequencies_used_;
-  }
-
   DECLARE_VIRTUAL_TRACE();
 
  private:
   friend class SensorProviderProxy;
   friend class SensorReadingUpdaterContinuous;
   friend class SensorReadingUpdaterOnChange;
   SensorProxy(device::mojom::blink::SensorType, SensorProviderProxy*, Page*);
 
   // Updates sensor reading from shared buffer.
   void UpdateSensorReading();
@@ skipping 12 matching lines @@
   // 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 OnAnimationFrame(double timestamp);
+
+  void OnPollingTimer(TimerBase*);
+  // Starts polling timer if needed (continuous reporting, initialized, not
+  // suspended and has configurations added).
+  void UpdatePollingStatus();
 
   device::mojom::blink::SensorType type_;
   device::mojom::blink::ReportingMode mode_;
   Member<SensorProviderProxy> provider_;
   using ObserversSet = HeapHashSet<WeakMember<Observer>>;
   ObserversSet observers_;
 
   device::mojom::blink::SensorPtr sensor_;
   device::mojom::blink::SensorConfigurationPtr default_config_;
   mojo::Binding<device::mojom::blink::SensorClient> client_binding_;
 
   enum State { kUninitialized, kInitializing, kInitialized };
   State state_;
   mojo::ScopedSharedBufferHandle shared_buffer_handle_;
   mojo::ScopedSharedBufferMapping shared_buffer_;
   bool suspended_;
   device::SensorReading reading_;
   std::pair<double, double> frequency_limits_;
 
-  Member<SensorReadingUpdater> reading_updater_;
   WTF::Vector<double> frequencies_used_;
-  double last_raf_timestamp_;
+  TaskRunnerTimer<SensorProxy> polling_timer_;
 
   using ReadingBuffer = device::SensorReadingSharedBuffer;
   static_assert(
       sizeof(ReadingBuffer) ==
           device::mojom::blink::SensorInitParams::kReadBufferSizeForTests,
       "Check reading buffer size for tests");
 };
 
 }  // namespace blink
 
 #endif  // SensorProxy_h