Check context status before recreating platform destination

Changing the channel count in the RealtimeAudioDestinationHandler will
trigger the recreation of the platform destination. This in turn can
activate the audio rendering thread.

This CL adds a check to prevent this from happening after the handler
is garbage collected.

(cherry picked from commit 4997f2b)

Bug: 1497859
Test: Locally confirmed with ASAN
Change-Id: I5d2649f3fd3639779ae40b0ca4ef2fe305653421
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4995928
Commit-Queue: Hongchan Choi <hongchan@chromium.org>
Reviewed-by: Michael Wilson <mjwilson@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1217868}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5004961
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/5993@{#1520}
Cr-Branched-From: 5113507-refs/heads/main@{#1192594}

third_party/blink/renderer/modules/webaudio/realtime_audio_destination_handler.cc

@@ -118,12 +118,21 @@ void RealtimeAudioDestinationHandler::SetChannelCount(
   uint32_t old_channel_count = ChannelCount();
   AudioHandler::SetChannelCount(channel_count, exception_state);
 
-  // Stop, re-create and start the destination to apply the new channel count.
-  if (ChannelCount() != old_channel_count && !exception_state.HadException()) {
-    StopPlatformDestination();
-    CreatePlatformDestination();
-    StartPlatformDestination();
+  // After the context is closed, changing channel count will be ignored
+  // because it will trigger the recreation of the platform destination. This
+  // in turn can activate the audio rendering thread.
+  AudioContext* context = static_cast<AudioContext*>(Context());
+  CHECK(context);
+  if (context->ContextState() == AudioContext::kClosed ||
+      ChannelCount() == old_channel_count ||
+      exception_state.HadException()) {
+    return;
   }
+
+  // Stop, re-create and start the destination to apply the new channel count.
+  StopPlatformDestination();
+  CreatePlatformDestination();
+  StartPlatformDestination();
 }
 
 void RealtimeAudioDestinationHandler::StartRendering() {