Chromium Embedded Framework
In relation to Valve
The Steam client on Windows and OS X uses a customized version of CEF to render web content.
The Source code for Valve's usage of the Chromium Embedded Framework can be downloaded as a ZIP archive (783 MB, 24th April 2012).
A patch for revision 465 of the CEF codebase is available on pastebin (280 KB) that will apply Valve's changes. (Note, this patch does not include any changes that may have been made to the Chromium codebase.)