fix ScenePlaybackDetector.IsPlaying is still false when disable Domain Reloading

Author: kyubuns

Assets/Plugins/UniRx/Scripts/UnityEngineBridge/ScenePlaybackDetector.cs

@@ -54,9 +54,28 @@ static ScenePlaybackDetector()
         {
 #if UNITY_2017_2_OR_NEWER
             EditorApplication.playModeStateChanged += e =>
+            {
+                if (e == PlayModeStateChange.ExitingEditMode)
+                {
+                    AboutToStartScene = true;
+                }
+                else
+                {
+                    AboutToStartScene = false;
+                }
+
+                if (e == PlayModeStateChange.EnteredPlayMode)
+                {
+                    IsPlaying = true;
+                }
+
+                if (e == PlayModeStateChange.ExitingPlayMode)
+                {
+                    IsPlaying = false;
+                }
+            };
 #else
             EditorApplication.playmodeStateChanged += () =>
-#endif
             {
                 // Before scene start:          isPlayingOrWillChangePlaymode = false;  isPlaying = false
                 // Pressed Playback button:     isPlayingOrWillChangePlaymode = true;   isPlaying = false
@@ -77,6 +96,7 @@ static ScenePlaybackDetector()
                     IsPlaying = false;
                 }
             };
+#endif
         }
     }
 }