Fix preserving currently visible slider

Flag: com.android.systemui.volume_redesign
Bug: 369994956
Test: atest VolumeDialogSlidersInteractorTest
Test: manual on the tablet. Join the call to force the dialog to show
media and call sliders at the same time. Adjust any volume.

Change-Id: Ib6445bd8e02abab9974d1478a8e38c2342faaf58
diff --git a/packages/SystemUI/multivalentTests/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractorTest.kt b/packages/SystemUI/multivalentTests/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractorTest.kt
index 3f995c6..87d782e 100644
--- a/packages/SystemUI/multivalentTests/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractorTest.kt
+++ b/packages/SystemUI/multivalentTests/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractorTest.kt
@@ -172,9 +172,9 @@
                 runCurrent()
 
                 assertThat(slidersModel!!.slider)
-                    .isEqualTo(VolumeDialogSliderType.Stream(AudioManager.STREAM_MUSIC))
+                    .isEqualTo(VolumeDialogSliderType.Stream(AudioManager.STREAM_SYSTEM))
                 assertThat(slidersModel!!.floatingSliders)
-                    .containsExactly(VolumeDialogSliderType.Stream(AudioManager.STREAM_SYSTEM))
+                    .containsExactly(VolumeDialogSliderType.Stream(AudioManager.STREAM_MUSIC))
             }
         }
     }
diff --git a/packages/SystemUI/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractor.kt b/packages/SystemUI/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractor.kt
index c904ac5..690f9ef 100644
--- a/packages/SystemUI/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractor.kt
+++ b/packages/SystemUI/src/com/android/systemui/volume/dialog/sliders/domain/interactor/VolumeDialogSlidersInteractor.kt
@@ -63,7 +63,7 @@
                 LinkedHashSet(sliderTypes)
             }
             .runningReduce { sliderTypes, newSliderTypes ->
-                newSliderTypes.apply { addAll(sliderTypes) }
+                sliderTypes.apply { addAll(newSliderTypes) }
             }
             .map { sliderTypes ->
                 VolumeDialogSlidersModel(