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This CL updates the expiry of histograms that are bound to expire soon.
It also updates the descriptions since the semantics of the histograms
changed in place after commit a5484e63.

Bug: 1144816
Change-Id: I0eaf28a4f59c7d5803dcda9acd0f36e6678e8bab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2527507Reviewed-by: Ilya Sherman <isherman@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826288}