Deactivate the audio session after a call ends using the AVAudioSessionSetActiveOptionNotifyOthersO…

webrtc/modules/audio_device/ios/audio_device_ios.mm

Index: webrtc/modules/audio_device/ios/audio_device_ios.mm
diff --git a/webrtc/modules/audio_device/ios/audio_device_ios.mm b/webrtc/modules/audio_device/ios/audio_device_ios.mm
index f26e9f1cc7463657a2646aa28f4789cc9bbe73b2..b94ea17b7f62a96d78be7f2f85f92a18d8630edb 100644
--- a/webrtc/modules/audio_device/ios/audio_device_ios.mm
+++ b/webrtc/modules/audio_device/ios/audio_device_ios.mm
@@ -86,13 +86,21 @@ static void ActivateAudioSession(AVAudioSession* session, bool activate) {
     NSError* error = nil;
     BOOL success = NO;
 
-    // Deactivate the audio session and return if |activate| is false.
     if (!activate) {
-      success = [session setActive:NO error:&error];
+      // Deactivate the audio session using an extra option and then return.
+      // AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation is used to
+      // ensure that other audio sessions that were interrupted by our session
+      // can return to their active state. It is recommended for VoIP apps to
+      // use this option.
+      success = [session

[tkchin_webrtc, 2015/11/16 21:40:34]

nit: 
maybe just break it onto next line (you can copy/paste the text to see the
formatting, it's not even width in CR tool)
success =
    [session setActive:NO
           withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation
                 error:&error];

[henrika_webrtc, 2015/11/17 13:52:32]

withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation does not fit
within the 80-char limit if I do so. Keeping as is unless you think I should
break 80 here.

+            setActive:NO
+          withOptions:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation
+                error:&error];
       RTC_DCHECK(CheckAndLogError(success, error));
       return;
     }
 
+    // Go ahead and active our own audio session since |activate| is true.
     // Use a category which supports simultaneous recording and playback.
     // By default, using this category implies that our app’s audio is
     // nonmixable, hence activating the session will interrupt any other