WIP patch: https://codereview.chromium.org/1898233002/

Down prioritized, as we've got data showing that other interventions will help a lot here.

Re-prioritized, as this is blocking for Progressive Web Metrics.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/06f261ea4b8db484ffd50d96676dd34e203fa626

commit 06f261ea4b8db484ffd50d96676dd34e203fa626
Author: tdresser <tdresser@chromium.org>
Date: Thu Jul 07 18:29:54 2016

Report expected task queueing time via UMA

Reported to:
RendererScheduler.ExpectedTaskQueueingDuration

This is recorded for each 5 second window. This is the expected
queueing duration for a high priority task.

BUG= 607151 
TEST=QueueingTimeEstimatorTest

Review-Url: https://codereview.chromium.org/1898233002
Cr-Commit-Position: refs/heads/master@{#404185}

[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/BUILD.gn
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/components_tests.gyp
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/BUILD.gn
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[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/queueing_time_estimator.h
[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/queueing_time_estimator_unittest.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/task_queue_manager.cc
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[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/task_time_tracker.h
[delete] https://crrev.com/ffaecc8ff3be5cdd883e5a51b19acc04cb40a4b4/components/scheduler/base/test_always_fail_time_source.cc
[delete] https://crrev.com/ffaecc8ff3be5cdd883e5a51b19acc04cb40a4b4/components/scheduler/base/test_always_fail_time_source.h
[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/test_count_uses_time_source.cc
[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/test_count_uses_time_source.h
[add] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/test_task_time_tracker.h
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/time_domain.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/time_domain.h
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/base/time_domain_unittest.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/child/scheduler_helper.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/child/scheduler_helper.h
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/renderer/auto_advancing_virtual_time_domain_unittest.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/renderer/idle_time_estimator_unittest.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/renderer/renderer_scheduler_impl.cc
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/renderer/renderer_scheduler_impl.h
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/components/scheduler/scheduler.gypi
[modify] https://crrev.com/06f261ea4b8db484ffd50d96676dd34e203fa626/tools/metrics/histograms/histograms.xml