virtual_oss is not a runtime dependency for chromium. You need to configure it before using, so it won't help you if it's installed with chromium. And it's useless with ALSA(alsa-lib supports asound.conf) and PulseAudio, both can select audio input/output. Now it forced to be installed even if won't be used. virtual_oss dependency should be removed or be optional and enabled by default with only SNDIO backend.
*** This bug has been marked as a duplicate of bug 255994 ***
(In reply to Li-Wen Hsu from comment #1) Don't know how it happened, two identical bug reports with the same reported time. Thanks for closing this.