webrtc/datachannel/multiple-connections.html is sometimes timing out after M120 upgrade

https://bugs.webkit.org/show_bug.cgi?id=267281
rdar://problem/120725671

Reviewed by Eric Carlson.

We were sometimes deadlocking when:
- main thread asks something to the webrtc stack by hopping to the signalling thread.
- signaling thread is destroying the LibWebRTCAudioModule which was calling callOnMainThreadAndWait to do its cleanup.

Instead of cleaning things in LibWebRTCAudioModule destructor synchronsouly, we are doing the clean-up asynchronously in LibWebRTCAudioModule::Terminate.
Setting m_logTimer to nullptr there is fine since m_logTimer is used in Start/Stop via callOnMainThread.

* Source/WebCore/platform/mediastream/libwebrtc/LibWebRTCAudioModule.cpp:
(WebCore::LibWebRTCAudioModule::~LibWebRTCAudioModule):
(WebCore::LibWebRTCAudioModule::Terminate):
* Source/WebCore/platform/mediastream/libwebrtc/LibWebRTCAudioModule.h:

Canonical link: https://commits.webkit.org/272828@main

Author: youennf

Source/WebCore/platform/mediastream/libwebrtc/LibWebRTCAudioModule.cpp

@@ -47,9 +47,15 @@ LibWebRTCAudioModule::LibWebRTCAudioModule()
 
 LibWebRTCAudioModule::~LibWebRTCAudioModule()
 {
-    callOnMainThreadAndWait([&] {
+    ASSERT(!m_logTimer);
+}
+
+int32_t LibWebRTCAudioModule::Terminate()
+{
+    callOnMainThread([this, protectedThis = rtc::scoped_refptr<webrtc::AudioDeviceModule>(this)] {
         m_logTimer = nullptr;
     });
+    return 0;
 }
 
 int32_t LibWebRTCAudioModule::RegisterAudioCallback(webrtc::AudioTransport* audioTransport)

Source/WebCore/platform/mediastream/libwebrtc/LibWebRTCAudioModule.h

@@ -77,7 +77,7 @@ class LibWebRTCAudioModule : public webrtc::AudioDeviceModule {
 
     int32_t ActiveAudioLayer(AudioLayer*) const final { return shouldNotBeCalled(-1); }
     int32_t Init() final { return 0; }
-    int32_t Terminate() final { return 0; }
+    int32_t Terminate() final;
     bool Initialized() const final { return true; }
     int16_t PlayoutDevices() final { return 0; }
     int16_t RecordingDevices() final { return 0; }