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A following CL will integrate this new view with the existing tray UI behind a
flag.

Old UI:
https://screenshot.googleplex.com/piFt6475aT4

New UI:
https://screenshot.googleplex.com/80T0oZeapqJ

TEST=unit test + verified manually
BUG=921267

Change-Id: Ie82e3e0144bfa1465088af06564aab3588a9e8a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1669441
Commit-Queue: Tim Song <tengs@chromium.org>
Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672731}