[scheduler] Further breakdown of task duration metrics.

Record task duration for each minute for the first five minutes after
backgrounding the renderer and the rest of the time after five minutes.
Also record these metrics for first three minutes after foregrounding
the renderer and for the rest of the time after three minutes.

R=skyostil@chromium.org,rkaplow@chromium.org

Change-Id: I094a74763897ccba356df5176425808359bc410b
Reviewed-on: https://chromium-review.googlesource.com/552547
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#483672}

• third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc[diff]
• third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.h[diff]
• tools/metrics/histograms/histograms.xml[diff]