Reland "Unify input delay computations"

This is a reland of 5d945012c69d754ad5b659008eac95e5f0affabc

Original change's description:
> Unify input delay computations
>
> This CL unifies the timestamp computations for FID as reported to UMA and FID as
> exposed in the Web Perf API. It moves the UMA reporting from the
> PageWidgetDelegate to the EventTiming class. After this CL, the same types of
> events are logged by both the UMA metric and the webexposed metric. In addition,
> this CL removes the check that there are default actions or event handlers from
> EventTiming, which means that now the webexposed API will expose events even if
> they have no associated event handlers. In particular, this means that a click
> will now trigger mousedown, click, and mouseup entries, in that order. This is
> reflected in changes to the layout tests.
>
> Bug: 897656
> Change-Id: Ibeee0ffe9ff1fc0df74585da96a8fd3a6f2d17dc
> Reviewed-on: https://chromium-review.googlesource.com/c/1334564
> Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
> Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
> Reviewed-by: Timothy Dresser <tdresser@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#610201}

TBR=dtapuska@chromium.org

Bug: 897656, 843184
Change-Id: I4d97f2731fe957696c0e908d5ef3493235b52d49
Reviewed-on: https://chromium-review.googlesource.com/c/1348254
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610499}
20 files changed