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navigationStart in NavigationTiming

From: Arvind Jain <arvind@google.com>
Date: Tue, 30 Apr 2013 19:07:40 -0700
Message-ID: <CAOYaDdOwTpv9LEQDRY_b0KpefoWnzsSxd933XVPBqA+ZRoZnPw@mail.gmail.com>
To: public-web-perf <public-web-perf@w3.org>
I've a question about the definition of navigationStart in the
specification (
http://www.w3.org/TR/navigation-timing/#dom-performancetiming-navigationstart
)

It says:
This attribute must return the time immediately after the user agent
finishes prompting to
unload<http://www.w3.org/TR/html5/browsers.html#prompt-to-unload-a-document>
the
previous document. If there is no previous document, this attribute must
return the same value as
fetchStart<http://www.w3.org/TR/navigation-timing/#dom-performancetiming-fetchstart>
.

The second part of this statement seems odd to me. In case the document in
question has redirects (e.g. same origin redirects), the value of
navigationStart will be very different if there was a previous document
that had to be unloaded vs. not.

The difference doesn't make sense.

This line was added on Oct 14. 2010. There is one discussion a day before
that
http://lists.w3.org/Archives/Public/public-web-perf/2010Oct/0024.html
which seems to have better text for this but the spec has something else.

I think this inconsistency happened as we revised the definition of
navigationStart, and we forgot to update the second part of the definition.

I checked Chrome and it does the right thing - I load
http://en.wikipedia.org/ in a new tab and it has a same origin redirect.
navigationStart is not equal to fetchStart in this case, and in fact occurs
before redirectStart which in my opinion is correct behavior.

How do we fix this?

Arvind
Received on Wednesday, 1 May 2013 02:08:12 UTC

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