Remove chromeFirstPaint from PerformanceTiming context

[miike]

Currently we rely on chrome.loadTimes to populate the chromeFirstPaint value for the iglu:org.w3/PerformanceTiming schema.

loadTimes is deprecated[1] in Chrome 64 and will be removed in Chrome 71 (release early in December 2018). Google recommend[2] replacing this with values from the PaintTiming spec/API instead though the spec for this is still in draft.

Once this is more widely implemented in browsers this could belong in it's own context rather than replacing the current first paint values.

[1] https://developers.google.com/web/updates/2017/12/chrome-loadtimes-deprecated

[alexanderdean]

Thanks for flagging miike. Per the comments on the commit:

• What is the impact of leaving this in till late this year?
• Is there any ETA on the new spec being implemented by the major browsers?

[alexanderdean]

Nudge miike

[miike]

Chrome currently has full support but the support in other browsers is still non-existent at this stage.

[bermannoah]

Hi there, any word on when the fix in #636 might get merged? Anything else that needs to be done? (I figured I'd ask in the issue since the PR says it's been de-scheduled pending conversation here.)

[alexanderdean]

Thanks for asking Noah Berman (@bermannoah) - assigning to Michael Hadam (@mhadam) to look into...

[miike]

I think this should be fine to remove now. If we want to grab paint values (in Chrome or other supported browsers) it makes sense to have these in a different paint specific context.