GitLab

While working on https://codereview.chromium.org/542733002/ to fix
issue 410276, a question came up about how important OpenPrevEntry was
to maintain; it made that CL more complex and for what users?

It turns out, it's not really used. See
https://groups.google.com/a/chromium.org/forum/#!topic/net-dev/wlMR_zNJ85k
for a discussion.

Let's remove it and save ourselves some headaches.

R=clamy@chromium.org
BUG=410276

Review URL: https://codereview.chromium.org/547513002

Cr-Commit-Position: refs/heads/master@{#293593}