194787 - lazily lay out/reflow pages with immediate onload redirects

Status: RESOLVED WONTFIX

(Core :: Layout, enhancement, P3)

Description

[Myk Melez [:myk] [@mykmelez]]

We should lazily lay out/reflow pages with immediate redirects in their onload
handler and only lay out if the handler requests the position of an element. 
Doing this would improve performance in certain edge cases, particularly
performance tests like i-Bench, and would make such tests between us and Safari
(which does this) more directly comparable.

Comment 1

[Boris Zbarsky [:bzbarsky]]

How do we determine whether an onload handler contains a redirect, much less an
immediate one?  (This is equivalent to the halting problem, no?  We could just
randomly guess, I suppose.)

Comment 2

[Myk Melez [:myk] [@mykmelez]]

I was under the impression that we already cancel paint when we detect an
immediate redirect, but perhaps I was mistaken and we merely unconditionally
defer paint until after the onload handler fires (thus having the effect of
canceling paint for immediate redirects). jrgm knows more.

Comment 3

[John Morrison]

I looked at this a bit. It seems to be implicit, not explicit.

Comment 4

[Jesse Ruderman]

See bug 572604 for a variant of this idea that doesn't require solving the halting problem.