Added audioSessionDidActivate and audioSessionDidDectivate

webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm

Index: webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm
diff --git a/webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm b/webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm
index 4ce24e7c3fd56b7d2472d91b236862c26dd8b860..8ebd640305a0bfd5b21a86a29eef1dad95382d95 100644
--- a/webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm
+++ b/webrtc/modules/audio_device/ios/objc/RTCAudioSession.mm
@@ -688,7 +688,7 @@ NSInteger const kRTCAudioSessionErrorConfiguration = -2;
   if (![self setConfiguration:webRTCConfig active:YES error:&error]) {
     RTCLogError(@"Failed to set WebRTC audio configuration: %@",
                 error.localizedDescription);
-    [self unconfigureWebRTCSession:nil];
+    // Don't call unconfigureWebRTCSession if the audio session wasn't configured successfully
     if (outError) {
       *outError = error;
     }
@@ -787,6 +787,22 @@ NSInteger const kRTCAudioSessionErrorConfiguration = -2;
   }
 }
 
+- (void)audioSessionDidActivate:(AVAudioSession *)session {
+  if (_session != session) {
+    RTCLogError(@"audioSessionDidActivate called on different AVAudioSession");
+  }
+  [self incrementActivationCount];
+  self.isActive = YES;
+}
+
+- (void)audioSessionDidDeactivate:(AVAudioSession *)session {
+  if (_session != session) {
+    RTCLogError(@"audioSessionDidDeactivate called on different AVAudioSession");
+  }
+  self.isActive = NO;
+  [self decrementActivationCount];
+}
+
 - (void)notifyDidBeginInterruption {
   for (auto delegate : self.delegates) {
     SEL sel = @selector(audioSessionDidBeginInterruption:);