After a few minutes of play, I noticed that my chair was slightly closer to my monitor. Dismissing this as nothing out of the ordinary, I pushed it back into place and resumed playing.
After a few more minutes I again noticed it had shifted a few inches forward. Puzzled, I stood up and watched the chair. At first, I saw nothing, but then I noticed a slight movement. Kneeling down to get a better look I found that my chair was, ever so slightly, moving forward, towards my monitor.
Suddenly, I realized what what happening.
The Chrome demo sucks so hard, it was literally sucking me and my chair towards the screen! I immediately quit and uninstalled the demo, noting that my chair had returned to its usual stationary state.
Beware, for the Chrome demo *really* sucks.