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This adds metrics for actions of the muted notification as well as stats
once the screen capture session ends.

Bug: 1131375
Change-Id: I47a5fc9bf6677f3cc248d727b9a95c4048983870
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2467941
Commit-Queue: Richard Knoll <knollr@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#822681}