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UMA metrics RecordVisibilityHistogram and UKM metrics
TabManager_TabLifetime are moved from TabActivityWatcher to
TabStatsTracker without changing its logic.

Bug: 1131349
Change-Id: Iee06e9ff87fb43293e62fd5d7b9d83af9437f205
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437087Reviewed-by: Thanh Nguyen <thanhdng@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Charles . <charleszhao@chromium.org>
Commit-Queue: Charles . <charleszhao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814018}