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Re: [ResourceTiming] The clock base to use in ResourceTiming is not defined

From: Philippe Le Hegaret <plh@w3.org>
Date: Mon, 30 Sep 2013 14:30:15 -0400
Message-ID: <1380565815.4763.23.camel@chacal>
To: Boris Zbarsky <bzbarsky@MIT.EDU>
Cc: "public-web-perf@w3.org" <public-web-perf@w3.org>
On Fri, 2013-09-27 at 22:42 -0400, Boris Zbarsky wrote:
> This is implementor feedback on 
> http://www.w3c-test.org/webperf/specs/ResourceTiming/
> 
> This document never defines the point that corresponds to time 0. 

All the timing attributes are using the DOMHighResTimeStamp type, which
is defined in High Resolution Time as follows:
[[
4.2 The DOMHighResTimeStamp Type

The DOMHighResTimeStamp type is used to store a time value measured
relative to the navigationStart attribute of the PerformanceTiming
interface [NavigationTiming], the start of navigation of the document,
or a time value that represents a duration between two
DOMHighResTimeStamps.
]]
http://www.w3.org/TR/2012/REC-hr-time-20121217/#sec-DOMHighResTimeStamp

Therefore, unless the attribute represents a duration (such as
PerformanceEntry.duration), the 0 time is relative to navigationStart.
This helps prevent clock skew or adjustment of the system clock.

Philippe
Received on Monday, 30 September 2013 18:30:21 UTC

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