Multithreading is not working on any Chromium-based browser, but it's working perfectly on Firefox.

**Describe the bug**
I was recently working on a practice project where my goal was to convert a webm video to mp4 format on the client side. Initially, I was able to achieve this using a single-threaded worker version. However, I later attempted to implement a multithreaded worker version, which unfortunately did not succeed. I spent some time troubleshooting to identify where I went wrong, but I couldn't pinpoint the issue.

To further investigate, I tested the conversion process in a playground environment, and I discovered that even the playground couldn't perform video conversion in multithreaded mode. Subsequently, I tried using different web browsers based on the Chromium engine, but they all failed in this aspect. Surprisingly, Firefox was the only browser that successfully executed the multithreaded video conversion.

**To Reproduce**
Anyone can reproduce this scenario from [FFMpeg PlayGround](https://ffmpegwasm.netlify.app/playground/). Just need to enable the Use Multithreading flag. Transcoding process will be stuck at 0%.

**Expected behavior**
The expected behavior involves the successful execution of multithreaded video conversion across various web browsers, including Chromium-based ones.

**Some Screenshots about this issue**

**Desktop**
- OS: Windows 11
- Browser: Chrome v117.0.5938.150, Microsoft Edge v117.0.2045.47, Vivaldi v6.2.3105.54, Firefox v117.0.1