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* Add const to various locally-const variables
* Remove const from function parameters
* Consistently compute result validity before setting the result, in
  preparation for making the latter conditional on the former
* Follow style guide better
* Reduce some deep indentation
* Brevity

None of these changes are intended to affect functionality.

Bug: none
Change-Id: I134e055904630f30054baafaa4b6cdb23d4eb16b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2585365
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835899}