navigationStart and the actual start of the navigation

Hello,

navigationStart for navigations without the previous document is described
in [1] as follows:

"If there is no previous document, this attribute must return the time the
current document is created."

What does "time the current document is created" mean? If read in terms of
terminology we use in Chromium/Blink, that would be the time when we start
loading the page in the renderer.

But this can happen long time after the "open link in new tab" button is
clicked. For instance, on Android spawning a new renderer takes significant
time. Under current definition, the time needed to spawn the renderer would
not be represented in the reported values.

Would it make sense to define "navigationStart" as follows:

"This attribute must return the time when the user agent determines that
the navigation will happen. For navigations from existing documents, this
is the time when the user agent finishes prompting to unload the previous
document."

?

Relevant discussion in the Chromium bug tracker: http://crbug.com/376004 .

Wdyt?

Cheers,
Przemek

[1]
https://dvcs.w3.org/hg/webperf/raw-file/tip/specs/NavigationTiming/Overview.html