Tab Search: Add last_active_time_ticks to tab_search.mojom.Tab

last_active_time_ticks is used to sort recent tabs.

Bug: 1099917
Change-Id: If5c224729e39c20ceda48a3d81b6e171b92be731
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382655


Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Yuheng Huang <yuhengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805629}