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* Inline temps
* Style guide bans "0.f"
* Don't restate types
* Better Time/TimeDelta unit usage
* Simplify
* Improve comments
* Split separate DCHECK conditions
* Use const/constexpr more
* Eliminate unnecessary heap alloc

Bug: none
Change-Id: I4f7938318d436855f754ea262af268a0a95f414f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2359007
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798542}