GitLab

Adds additional timing metrics for the mute notifications feature:
- How much time passes before the user takes an action on the
  notification
- How long a screen capture session lasts
- How much time passes from start of a session until the user reveals
  notification content again

Bug: 1131375
Change-Id: I70e99cfe5f5726c4372930df84b3a90c37970629
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2617942Reviewed-by: Brian White <bcwhite@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Richard Knoll <knollr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843123}