The FX_PREFERENCES_CATEGORY_OPENED probe must be extended to version 59 to support the fallback "forked" preference implementation (in-content-old). The switchToAdvancedSubPane within utilityOverlay's openPreferences must also remain until the fallback has been removed (bug 1349689). Patch co-authored by Zack Herrick <herrickz@msu.edu> and Ziyan Long <lzylong@gmail.com>. MozReview-Commit-ID: 1sx0Wj15yM7