Revert of UTF-8 detector for pages missing encoding info (patchset #12 id:210001 of https://codereview.chromium.org/1721373002/ )

Reason for revert:
Causes jetstream perf test to fail.
crbug.com/603558

Original issue's description:
> UTF-8 detector for pages missing encoding info
>
> Experiment crbug.com/518968 shows that about 30% of the pages
> missing character encoding information are encoded in UTF-8.
> This CL runs a quick one-pass scan against them to check if
> they are encoded in UTF-8. It helps get the encoding right
> for 30% of the pages without having to turn on full auto-encoding
> detection logic which is disabled due to slow performance.
>
> BUG=583549
> TEST=Layout test: fast/encoding/unlabelled-non-ascii-utf8.html
>
> Committed: https://crrev.com/2af3917eb9ca14b263116d664a8257ae69680610
> Cr-Commit-Position: refs/heads/master@{#387209}

TBR=esprehn@chromium.org,aelias@chromium.org,jshin@chromium.org,tkent@chromium.org,jinsukkim@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=583549

Review URL: https://codereview.chromium.org/1888083002

Cr-Commit-Position: refs/heads/master@{#387332}
11 files changed