Strange CSS rules setting IDs and classes to display:none

After updating to 3.7.1, I noticed things had gone missing from my site. My sidebar text widgets aren’t displaying, nor are the social media share buttons displayed on my single posts.

I deactivated all plugins and switched to the Twenty Eleven theme. My usual theme is a child of Twenty Eleven.

I used Chrome’s “Inspect Element” to see what was going on, and I found a bunch of CSS rules like this one:

.favicon-twitter, .favorite-twitter, .fb-activity-module, .fb-button, .fb-cont, .fb-custom-share, .fb-footer-recommend, .fb-icon, .fb-info, .fb-like, .fb-like-box, .fb-like-box-wrapper, .fb-like-buttons, .fb-like-holder, .fb-like-widget, .fb-outer, .fb-pageFeed, .fb-promo, .fb-recommend, .fb-share {
display: none;

The above was present even with NO plug-ins activated and using the Twenty Eleven theme.

I cannot find the source of this code either. Usually Chrome provides a link to the line in whatever CSS file it is showing. Not this time.

Can anyone tell me what’s going on?

Thanks in advance.