From a quick codesearch, this appears to be unused. (Came up in a recent refactoring as dependent code that needed to be changed).
The following revision refers to this bug: https://chromium.googlesource.com/chromium/src.git/+/8d3b098da65e0639a6efcc399af7cb00c379c343 commit 8d3b098da65e0639a6efcc399af7cb00c379c343 Author: Eric Roman <eroman@chromium.org> Date: Fri Apr 06 17:40:09 2018 Delete //chrome/browser/net/firefox_proxy_settings* Bug: 814849 Change-Id: I0d6b10c038d0d7d77ced05ad7a5246803803d0e8 Reviewed-on: https://chromium-review.googlesource.com/998844 Commit-Queue: Helen Li <xunjieli@chromium.org> Reviewed-by: Helen Li <xunjieli@chromium.org> Cr-Commit-Position: refs/heads/master@{#548844} [modify] https://crrev.com/8d3b098da65e0639a6efcc399af7cb00c379c343/chrome/browser/BUILD.gn [delete] https://crrev.com/1f976f747362c3f11b7e0e4ac93df6dfafa3818c/chrome/browser/net/firefox_proxy_settings.cc [delete] https://crrev.com/1f976f747362c3f11b7e0e4ac93df6dfafa3818c/chrome/browser/net/firefox_proxy_settings.h [delete] https://crrev.com/1f976f747362c3f11b7e0e4ac93df6dfafa3818c/chrome/browser/net/firefox_proxy_settings_unittest.cc [modify] https://crrev.com/8d3b098da65e0639a6efcc399af7cb00c379c343/chrome/test/BUILD.gn
Comment 1 by eroman@chromium.org
, Apr 5 2018