[Sensors] Implement sensor data polling

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/page/PageVisibilityObserver.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;
 
 // 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 device::mojom::blink::SensorClient
+    , public PageVisibilityObserver {

[haraken, 2016/09/08 11:07:13]

Sensor is already a PageVisibilityObserver. Can we avoid making SensorProxy a
PageVisibilityObserver?

[Mikhail, 2016/09/08 11:24:48]

Tim raised the same concern at https://codereview.chromium.org/2121313002/. 
Looks like I indeed need to find an alternate solution..

+    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 (for 'ONCHANGE' reporting mode).
         virtual void onSensorReadingChanged() {}
@@ skipping 27 matching lines @@
 
     const Reading& reading() const { return m_reading; }
 
     // Updates internal reading from shared buffer.
     void updateInternalReading();
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     friend class SensorProviderProxy;
-    SensorProxy(device::mojom::blink::SensorType, SensorProviderProxy*);
+    SensorProxy(device::mojom::blink::SensorType, Page*, SensorProviderProxy*);
 
     // device::mojom::blink::SensorClient overrides.
     void RaiseError() override;
     void SensorReadingChanged() override;
 
+    // PageVisibilityObserver overrides.
+    void pageVisibilityChanged() override;
+
     // Generic handler for a fatal error.
     void handleSensorError();
 
     void onSensorCreated(device::mojom::blink::SensorReadBufferPtr, device::mojom::blink::SensorClientRequest);
 
     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;
     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;
 };
 
 } // namespace blink
 
 #endif // SensorProxy_h