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This CL implements the stale-frame metrics that measure the undesirably
prolonged presentation time due to frame dropping. The metrics are
reported under the Graphics.Smoothness.Stale.* (staleness of each frame)
and Graphics.Smoothness.MaxStale.* (maximum staleness per interaction).

Bug: 1092949
Change-Id: Id2e3d616bfa4362fd8f4b6db4fedb23290d6cba6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490385Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Commit-Queue: Mingjing Zhang <mjzhang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827475}