bfcache: triage unit_tests

All the tests are failing for the same reason. The NavigatonSimulator
needs to be updated to take into account the navigations using the
BackForwardCache.

Bug: 989924
Change-Id: If79b33ca9217771e073b06c5fab5b020d0ad598d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1738375Reviewed-by: Arthur Hemery <ahemery@chromium.org>
Commit-Queue: Arthur Hemery <ahemery@chromium.org>
Auto-Submit: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#684314}

testing/buildbot/filters/bfcache.unit_tests.filter

 # These tests currently fail when run with --enable-features=BackForwardCache
+
+# Nullptr exception in TestNavigationURLLoader::CallOnresponseStarted().
+#
+# Updating the NavigationSimulator is needed to take into account the ones using
+# the BackForwardCache.
+#
+# See https://crbug.com/989924
 -BackFwdMenuModelTest.BasicCase
 -BackFwdMenuModelTest.ChapterStops
 -DownloadRequestLimiterTest.HistoryBack