Trying to move RecordDispatchingDelay() from content/browser/service_worker_metrics.h to content/common/service_worker.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/f33c1de7a02b3bdffe32858d424acfc568918a2b

commit f33c1de7a02b3bdffe32858d424acfc568918a2b
Author: Matt Falkenhagen <falken@chromium.org>
Date: Wed Jun 27 02:34:13 2018

service worker: Remove site suffix UMA for EventDispatchingDelay.

I don't recall ever using the site suffix breakdowns and they aren't
worth the complexity:
* Hardcoded sites didn't scale well. Nowadays we should use UKM if appropriate.
* It's unclear why we used the site suffixes for this particular UMA
and not the rest.
* This pattern resulted in (# event types) * (# of sites) histograms.

This doesn't change the semantic of the histogram, and just folds the
breakdown into the parent histogram, so no renaming is done.

Bug:  852668 
Change-Id: I5a090967a0d351f1291c67b37a071f77b324ce54
Reviewed-on: https://chromium-review.googlesource.com/1113378
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570639}
[modify] https://crrev.com/f33c1de7a02b3bdffe32858d424acfc568918a2b/content/browser/service_worker/service_worker_metrics.cc
[modify] https://crrev.com/f33c1de7a02b3bdffe32858d424acfc568918a2b/content/browser/service_worker/service_worker_metrics.h
[modify] https://crrev.com/f33c1de7a02b3bdffe32858d424acfc568918a2b/content/browser/service_worker/service_worker_version.cc
[modify] https://crrev.com/f33c1de7a02b3bdffe32858d424acfc568918a2b/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/de55e81dd70ed184d14f15f14efb33b2d9ae901d

commit de55e81dd70ed184d14f15f14efb33b2d9ae901d
Author: Kenichi Ishibashi <bashi@chromium.org>
Date: Mon Jul 02 06:57:22 2018

Record EventDispatchingDelay_FETCH_SUB_RESOURCE in S13nServiceWorker path

Before this CL we didn't record EventDispatchingDelay_FETCH_SUB_RESOURCE
when S13nServiceWorker is enabled because sub resource loading
doesn't go browser process. Record the metric in
ServiceWorkerSubresourceLoader.

Bug:  852668 
Change-Id: I3e7b2e833dda9d73f5b09917018e69275f29910c
Reviewed-on: https://chromium-review.googlesource.com/1113157
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571828}
[modify] https://crrev.com/de55e81dd70ed184d14f15f14efb33b2d9ae901d/content/renderer/service_worker/service_worker_subresource_loader.cc
[modify] https://crrev.com/de55e81dd70ed184d14f15f14efb33b2d9ae901d/content/renderer/service_worker/service_worker_subresource_loader.h
[modify] https://crrev.com/de55e81dd70ed184d14f15f14efb33b2d9ae901d/tools/metrics/histograms/histograms.xml