Firefox, Gmail, and the flash plug-in

My computer seemed slow. Everything was sluggish even though the "only thing" I was using was the Firefox browser. I did have several tabs open, but none that I knew to be media or script intensive. Yet, there was slowness. A quick glance at the task manager revealed that FlashPlayer plugin was consuming an entire core of my processor, which surprised me, since nothing should've been playing any videos.

So I killed it.

Processor seemed to go idle, things became a little snappier. Nothing seemed to have been affected. How is that possible? Was there a virus or trojan of some sort, I wondered. I got my answer when I tabbed back to my open gmail page. There, on the top, like an epiphany was displayed a bar across the tab: "Flash player plugin has crashed. Click here to relaunch page".

"What?"

Slowly, the wheels of thought groaned into motion: what is it on gmail's page that *might* use flash? Video / web-calling and Chatting seemed possible suspects. So I checked gmail's settings to see what was on, and if anything was using flash. Sure enough, clicking on chat settings showed me the following option:

Sounds:

Sounds on - Play a sound notification when new chat messages arrive. Requires Flash.

Sounds off

changed to "sounds off".  Recap: it was Flash player, in the Gmail tab, with the inappropriate chat settings. Clue!