Revert "[EventTiming] Ship First Input Timing on main frames"

This reverts commit 1ff422d8a30a34713c652508fc170f75120460a1.

Reason for revert: Will reland shipping First Input Timing once we are sure it's going to ship. For now, let's unship.

Original change's description:
> [EventTiming] Ship First Input Timing on main frames
> 
> Intent to ship:
> https://groups.google.com/a/chromium.org/forum/?utm_medium=email&utm_source=footer#!msg/blink-dev/LN92hkaKCzw/Y-ryVxu5AgAJ
> 
> Bug: 823744, 841224
> Change-Id: Ic4d3d67facd0d717b929b9798650eb502057fea6
> Reviewed-on: https://chromium-review.googlesource.com/c/1368826
> Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
> Reviewed-by: Timothy Dresser <tdresser@chromium.org>
> Reviewed-by: Yoav Weiss <yoavweiss@chromium.org>
> Reviewed-by: Yoav Weiss <yoav@yoav.ws>
> Cr-Commit-Position: refs/heads/master@{#625684}

TBR=yoav@yoav.ws,tdresser@chromium.org,npm@chromium.org,yoavweiss@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 823744, 841224
Change-Id: I4c95a1fd789793c240a35580f612627a0bc7af13
Reviewed-on: https://chromium-review.googlesource.com/c/1460428
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630528}
8 files changed