Most of the checks are unnecessary
Created attachment 270269 [details] patch
http://trac.webkit.org/changeset/195871
It looks like this patch may have caused 4 tests to fail: https://build.webkit.org/results/Apple%20El%20Capitan%20Release%20WK2%20(Tests)/r195871%20(2937)/results.html
Reverted r195871 for reason: Caused several layout tests to time out Committed r195909: <http://trac.webkit.org/changeset/195909>
Relanded in http://trac.webkit.org/changeset/196023 with 1 minute timer to avoid suspending tests that explicitly set page to non-visible state.