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* Improve comments
* Make DEPS block "third_party/abseil-cpp" and "absl" both
* Update formal "allowed on" date to date this lands
* Remove visibility restrictions

Bug: 1096380
Change-Id: I10f615cfd02c397a988f73e4548cdf2309b44b81
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327638
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793629}