GitLab

Update legacy code names and comments to use 'Assistant'.
Remove obsolete logics.

Bug: b/140823590
Test: Run existing tests
Change-Id: Ie5647e85b0030c2cddfa1dfeab86c752ab6148f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808091Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Yue Li <updowndota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697020}