Robot favicon (image/png) is currently only used in about:robots
(browser/base/content/aboutRobots.xhtml), but we intend to re-use this
resource for indicating that the browser is under remote (robot) control.
MozReview-Commit-ID: 4eTNbAITPQx
--HG--
extra : rebase_source : 765e4e2d7abe95ecc48b6a55582bde73fb689d5e
