Trying to figure out the timeline of events of device-pixel-ratio. If you know some events, chime in the comments with links.
- 2006-04-21 - High DPI Web Sites. Proposal by Dave Hyatt for Webkit.
- 2007-06-08 - CORE-6912. Creation in the bug tracker of Opera
- 2008-04-07 - Anne van Kesteren mentions device-pixel-ratio as "You actually want the proprietary -webkit-device-pixel-ratio"
- 2009-01-19 - Announce from Dave Hyatt on www-style that it is implemented in Webkit. Robert O'Callahan noticed that it was not documented
- 2009-01-19 - Bug 474356 - Implement device-pixel-ratio (Mozilla Bug)
- 2010-09-13 - Closing Mozilla Bug 474356
- 2010-10-08 - CSS Viewport spec proposed by Rune Lillesveen on www-style
- 2011-06-04 - supported in Opera with ratio number in Presto 2.8
- 2012-01-25 - Proposal to standardize it at a CSS WG meeting.