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This CL adds snooze to Tab Group IPH. It will not be in effect
until Finch is set up on the server side.

Future CLs:
* Add UMA.
* Add multi-arm Finch experiments to test on/off snooze
  and snooze duration.

Bug: 1121399
Change-Id: I5d7396ad783c6da14fd33ed8d9d78e4b79179c21
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398940
Auto-Submit: Keren Zhu <kerenzhu@chromium.org>
Reviewed-by: Tommy Nyquist <nyquist@chromium.org>
Reviewed-by: Collin Baker <collinbaker@chromium.org>
Reviewed-by: Wei Li <weili@chromium.org>
Commit-Queue: Keren Zhu <kerenzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807991}