Funny timing. I noticed this first after I updated Chrome and thought it was a part of their new audio indicators feature which might have been a part of the release.
While researching this I discovered that you can see audio indicators right now (even in the stable release) by including "–enable-audible-notifications" in the commandline when running the program.
My understanding is that Chrome wants to roll out this feature, but there is no way to know if various plugins, including flash, are playing audio. If they show an indicator for only html5 A/V it will seem like a half-broken feature.
While researching this I discovered that you can see audio indicators right now (even in the stable release) by including "–enable-audible-notifications" in the commandline when running the program.