Remove SecurityFilterPeer

Per the discussion at loading-dev@chromium.org[1], it seems the class
is no longer needed. Let's try to remove it.

1: https://groups.google.com/a/chromium.org/forum/#!topic/loading-dev/1wWw7YmrCQY

Bug: 954090
Change-Id: I5b88fd5bbf228d6840401cc2eaaf26d251201981
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1571122
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652084}
7 files changed