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This is done by saving the expanded/collapsed state when the tab is switched and restoring it when the tab is reselected.

Bug: b/159308598
Change-Id: Ib2f9c511c96557291251ef4b723bd88e4aa1721c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362824
Commit-Queue: Michele Mancina <micantox@google.com>
Reviewed-by: Mathias Carlen <mcarlen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803454}