Clarify code guidelines

Change-Id: I06a780bb0f4964601d64ceb27330a6e5fc27de67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1919737
Reviewed-by: Emily Stark <[email protected]>
Commit-Queue: Darin Fisher <[email protected]>
Cr-Commit-Position: refs/heads/master@{#715921}
1 file changed