Add LCP phase breakdown to the Lighthouse docs

[adamraine]

Part of GoogleChrome/lighthouse#14891

[chrome-devrel-infra]

✅ Preview (static) for commit 79ebe5e available at https://pr-6125-static-dot-dcc-staging.uc.r.appspot.com/.

The following pages likely changed with this PR:

• https://pr-6125-static-dot-dcc-staging.uc.r.appspot.com/docs/lighthouse/performance/lighthouse-largest-contentful-paint/

[tunetheweb]

This page says LCP landed in Chrome 77, but doesn't say when this breakdown phase landed. There might be an expectation it's there from Chrome 77 too.

Suggestions:

• Remove references to Chrome 77 (it's so long ago who cares!)
• Consider adding a "From Lighthosue 10.2, Lighthouse will display the LCP element along with the phase breakdown...". That will get old too so maybe not needed (especially when references to Chrome 77 are gone)? What do you usually do here?

[adamraine]

Remove references to Chrome 77 (it's so long ago who cares!)

This works for me.

Consider adding a "From Lighthosue 10.2, Lighthouse will display the LCP element along with the phase breakdown...". That will get old too so maybe not needed (especially when references to Chrome 77 are gone)? What do you usually do here?

I'm generally opposed to calling out when a specific feature was added unless it's super important or a breaking change. This is just adding extra diagnostic information to an existing audit.

[tunetheweb]

LGTM!