--- a/dom/audiochannel/AudioChannelService.cpp
+++ b/dom/audiochannel/AudioChannelService.cpp
@@ -130,24 +130,16 @@ AudioChannelService::UnregisterType(Audi
   // The array may contain multiple occurrence of this appId but
   // this should remove only the first one.
   AudioChannelInternalType type = GetInternalType(aType, aElementHidden);
   mChannelCounters[type].RemoveElement(aChildID);
 
   // In order to avoid race conditions, it's safer to notify any existing
   // agent any time a new one is registered.
   if (XRE_GetProcessType() == GeckoProcessType_Default) {
-    // We only remove ChildID when it is in the foreground.
-    // If in the background, we kept ChildID for allowing it to play next song.
-    if (aType == AUDIO_CHANNEL_CONTENT &&
-        mActiveContentChildIDs.Contains(aChildID) &&
-        (!mActiveContentChildIDsFrozen &&
-          !mChannelCounters[AUDIO_CHANNEL_INT_CONTENT].Contains(aChildID))) {
-      mActiveContentChildIDs.RemoveElement(aChildID);
-    }
     SendAudioChannelChangedNotification();
     Notify();
   }
 }
 
 bool
 AudioChannelService::GetMuted(AudioChannelAgent* aAgent, bool aElementHidden)
 {
@@ -294,22 +286,18 @@ AudioChannelService::SendAudioChannelCha
     else if (!mChannelCounters[AUDIO_CHANNEL_INT_ALARM_HIDDEN].IsEmpty()) {
       higher = AUDIO_CHANNEL_ALARM;
     }
 
     else if (!mChannelCounters[AUDIO_CHANNEL_INT_NOTIFICATION_HIDDEN].IsEmpty()) {
       higher = AUDIO_CHANNEL_NOTIFICATION;
     }
 
-    // There is only one Child can play content channel in the background.
-    // And need to check whether there is any content channels under playing
-    // now.
-    else if (!mActiveContentChildIDs.IsEmpty() &&
-             mChannelCounters[AUDIO_CHANNEL_INT_CONTENT_HIDDEN].Contains(
-             mActiveContentChildIDs[0])) {
+    // Content channels play in background if just one is active.
+    else if (!mActiveContentChildIDs.IsEmpty()) {
       higher = AUDIO_CHANNEL_CONTENT;
     }
   }
 
   if (higher != mCurrentHigherChannel) {
     mCurrentHigherChannel = higher;
 
     nsString channelName;