Add MediaStream.active attribute

Source/modules/mediastream/MediaStream.h

Index: Source/modules/mediastream/MediaStream.h
diff --git a/Source/modules/mediastream/MediaStream.h b/Source/modules/mediastream/MediaStream.h
index 88db16bb3414650611f46d6bc71ce6d737abe4c1..9bca0356c58118a343664497e5fb5b29b084077c 100644
--- a/Source/modules/mediastream/MediaStream.h
+++ b/Source/modules/mediastream/MediaStream.h
@@ -66,9 +66,12 @@ public:
     MediaStreamTrackVector getVideoTracks() const { return m_videoTracks; }
     MediaStreamTrackVector getTracks();
 
+    bool active() const { return m_descriptor->active(); }
     bool ended() const;
     void stop();
 
+    DEFINE_ATTRIBUTE_EVENT_LISTENER(active);
+    DEFINE_ATTRIBUTE_EVENT_LISTENER(inactive);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(ended);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(addtrack);
     DEFINE_ATTRIBUTE_EVENT_LISTENER(removetrack);
@@ -100,6 +103,8 @@ private:
     virtual void addRemoteTrack(MediaStreamComponent*) override;
     virtual void removeRemoteTrack(MediaStreamComponent*) override;
 
+    bool emptyOrOnlyEndedTracks();
+
     void scheduleDispatchEvent(PassRefPtrWillBeRawPtr<Event>);
     void scheduledEventTimerFired(Timer<MediaStream>*);