Always ignore navigation in Document::detach() in LocalFrame::navigate()

      We already checked that FrameNavigation is enabled before trying to
schedule a LocationChange; however, it was possible to construct a
scenario with an opened window that would use the sync loading path and
bypass this check.

BUG=597532

Review URL: https://codereview.chromium.org/1840813002

Cr-Commit-Position: refs/heads/master@{#383627}