I'm going to create a follow-up for showing the implicit grid areas in the CSS grid inspector highlighter and resolve this once https://phabricator.services.mozilla.com/D21308 lands.
Bug 1526975 Comment 19 Edit History
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I'm going to create a follow-up for showing the implicit grid areas in the CSS grid inspector highlighter and resolve this once https://phabricator.services.mozilla.com/D21308 lands. See Bug 1553312 for showing the names of implicit grid areas.