Background-size: cover suddenly stopped working in Google Chrome?
I just ran into this problem in Chrome, too.
None of the above answers worked for me. Specifically, I was trying to set the <body> element background to background-size: cover. However, the background image would never extend vertically to fill the page.
After some trial and error, I found that setting the <html> element width and height to 100% fixed the problem in Chrome. (For what it's worth, changing the <body> element's width and height seemed to have no effect.)
In my css, I have the following rules to fix the issue:
html { width: 100%; height: 100%;}