UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.139 Safari/537.36

Steps to reproduce the problem:
part 1
1. Open devTools to network panel
2. Navigate to https://benhastings.github.io/serverTimingDemo/
3. click "default.css" and view the Timing tab to see the serverTiming metrics
4. In console, performance.getEntriesByType('resource')[0].serverTiming returns an empty array

part 2
1. Navigate to https://server-timing.firebaseapp.com/default.css
2. in console, performance.getEntriesByType('navigation')[0].serverTiming returns an array with the two values displayed in the TIming panel

What is the expected behavior?
resourceTiming entries should include the serverTiming metrics with the appropriate name, duration, and description (if supplied in the header)

What went wrong?
In Chrome 65, the resourceTiming entries did include entries for serverTiming when supplied.  At that point, they contained a name and description, but the duration was always zero regardless of what was supplied.

As soon as 66 was released, I tested to see if the duration was supplied, and found the entries missing altogether.

Did this work before? No 

Does this work in other browsers? Yes

Chrome version: 66.0.3359.139  Channel: stable
OS Version: OS X 10.12.6
Flash Version: 

I tested this in windows and macOS on 65, 66 and the latest nightly for Chromium (only on windows)
I'm very interested in this capability affording the opportunity for expanded response time metrics resolution for automated performance evaluation through puppeteer and other means.  

I went so far as to create the firebase app just to supply serverTiming entries and the github page to expose the resource deficit.  I am happy to help testing or troubleshooting further.