imported/w3c/web-platform-tests/dom/ranges/Range-mutations.html is flaky (sometimes timeouts) First known timeout is r189484. https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20(Tests)/r196216%20(13627)/results.html
The test filed under this bug has been passing consistently in the last 4000 revisions. The test was removed from expectations in r262797. Closing bug. Committed r262811: <https://trac.webkit.org/changeset/262811>