web-platform-tests have been running against GeckoView for a couple of months, and we've found that several tests in this component are unstable and need investigation.

Here is the state of disabled tests according to testing/web-platform/meta at revision 241af4dbb964

navigation-timing/nav2_test_navigation_type_reload.html
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1499003', '  bug 1550895 (frequently fails on geckoview)']
navigation-timing/nav2_test_redirect_server.html
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1499003', '  bug 1550895 (frequently fails on geckoview)']
resource-timing/idlharness.any.js
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1499003']
resource-timing/resource-timing-level1.sub.html
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1543604']
resource-timing/resource_timing.worker.js
    ['   Bug 1557495, Bug 1499003, Bug 1557492']
resource-timing/test_resource_timing.https.html
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1526212']
user-timing/measure_associated_with_navigation_timing.html
    ['  https://bugzilla.mozilla.org/show_bug.cgi?id=1461298', '  bug 1550895 (frequently fails on geckoview)']

Filing this bug to track the work needed to turn them all back on.