Electron: Add video and audio codecs

You have to do a custom build libchromiumcontent with custom ffmpeg_branding, currently we just use the chrome browser's setting since it is well tested. You can find more at https://github.com/atom/electron/issues/1595.

Ok, it looks like none of the existing ffmpeg_branding brands support ac3, and looking at vendor\chromium\src\third_party\ffmpeg\build_ffmpeg.py line 493 it looks like i need to add some flags to the ffmpeg build

# Google Chrome & ChromeOS specific configuration.
configure_flags['Chrome'].extend([
    '--enable-decoder=aac,h264,mp3',
    '--enable-demuxer=aac,mp3,mov',
    '--enable-parser=aac,h264,mpegaudio',
])

How is this done? Do I make a patch in patches\third_party\ffmpeg? Or am I on the completely wrong track?

What is the modern way of doing this? This issue seems pretty old so I'm sure things have changed.