Respond to CR.

// FREEBIE

Signal/src/call/Speakerbox/CallKitCallUIAdaptee.swift

@@ -261,17 +261,14 @@ final class CallKitCallUIAdaptee: NSObject, CallUIAdaptee, CXProviderDelegate {
         //        // Trigger the call to be ended via the underlying network service.
         //        call.endSpeakerboxCall()
 
-        // Synchronous to ensure call is terminated before call is displayed as "ended"
         self.callService.handleLocalHungupCall(call)
 
-        DispatchQueue.main.async {
         // Signal to the system that the action has been successfully performed.
         action.fulfill()
 
         // Remove the ended call from the app's list of calls.
         self.callManager.removeCall(call)
     }
-    }
 
     public func provider(_ provider: CXProvider, perform action: CXSetHeldCallAction) {
         AssertIsOnMainThread()

Signal/src/call/UserInterface/CallUIAdapter.swift

@@ -42,7 +42,6 @@ extension CallUIAdaptee {
         notificationsAdapter.presentMissedCall(call, callerName: callerName)
     }
 
-    // TODO: who calls this?
     internal func callBack(recipientId: String) {
         AssertIsOnMainThread()
 

Signal/src/call/WebRTCCallMessageHandler.swift

@@ -28,24 +28,23 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
     // MARK: - Call Handlers
 
     public func receivedOffer(_ offer: OWSSignalServiceProtosCallMessageOffer, from callerId: String) {
+        AssertIsOnMainThread()
         Logger.verbose("\(TAG) handling offer from caller:\(callerId)")
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
-        DispatchQueue.main.async {
-            _ = self.callService.handleReceivedOffer(thread: thread, callId: offer.id, sessionDescription: offer.sessionDescription)
-        }
+        self.callService.handleReceivedOffer(thread: thread, callId: offer.id, sessionDescription: offer.sessionDescription)
     }
 
     public func receivedAnswer(_ answer: OWSSignalServiceProtosCallMessageAnswer, from callerId: String) {
+        AssertIsOnMainThread()
         Logger.verbose("\(TAG) handling answer from caller:\(callerId)")
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
-        DispatchQueue.main.async {
         self.callService.handleReceivedAnswer(thread: thread, callId: answer.id, sessionDescription: answer.sessionDescription)
     }
-    }
 
     public func receivedIceUpdate(_ iceUpdate: OWSSignalServiceProtosCallMessageIceUpdate, from callerId: String) {
+        AssertIsOnMainThread()
         Logger.verbose("\(TAG) handling iceUpdates from caller:\(callerId)")
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
@@ -54,29 +53,25 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
         // while the RTC iOS API requires a signed int.
         let lineIndex = Int32(iceUpdate.sdpMlineIndex)
 
-        DispatchQueue.main.async {
         self.callService.handleRemoteAddedIceCandidate(thread: thread, callId: iceUpdate.id, sdp: iceUpdate.sdp, lineIndex: lineIndex, mid: iceUpdate.sdpMid)
     }
-    }
 
     public func receivedHangup(_ hangup: OWSSignalServiceProtosCallMessageHangup, from callerId: String) {
+        AssertIsOnMainThread()
         Logger.verbose("\(TAG) handling 'hangup' from caller:\(callerId)")
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
 
-        DispatchQueue.main.async {
         self.callService.handleRemoteHangup(thread: thread)
     }
-    }
 
     public func receivedBusy(_ busy: OWSSignalServiceProtosCallMessageBusy, from callerId: String) {
+        AssertIsOnMainThread()
         Logger.verbose("\(TAG) handling 'busy' from caller:\(callerId)")
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
 
-        DispatchQueue.main.async {
         self.callService.handleRemoteBusy(thread: thread)
     }
-    }
 
 }