771221 - Navigation Timing API incorrectly reports first byte

Status: UNCONFIRMED

(Firefox :: General, defect)

Description

[saetaes]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:13.0) Gecko/20100101 Firefox/13.0.1.  (Also seen on Windows 7, Firefox 13)

Steps to reproduce:

First, get a server that sends a partial header before eventually serving the first byte.  This one works well:  https://github.com/jgrahamc/ttfb.  Load the page, and using the navigation timing API, calculate the first byte time, which is denoted as the delta between requestStart and responseStart.  

Actual results:

>>> window.performance.timing.responseStart - window.performance.timing.requestStart
1

Expected results:

>>> window.performance.timing.responseStart - window.performance.timing.requestStart
10000

This works as expected in other Navigation Timing-enabled browsers.