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Moves TabOpening protocol implementation and updates tests.

Bug: None
Change-Id: Iee5608fc34d288f3196dd77438825264add0f15c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1984307
Commit-Queue: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#732376}