I've noticed that we're getting a lot of ReconstructFramesForContent() calls while loading XUL documents; it turns out that we can squelch a bunch of these by simply making the PresShell ignore AttributeChanged notifications before the intial reflow has occurred. This ought to nominally improve new window performance, for example.

Yeah, the "morse code" for bringing up a new window shows about 40 attribute-change notifications wandering through the style system, so this can't hurt at all. (Did you want me to review?)

Comment on attachment 53446 [details] [diff] [review] diff -wu, only notify style set if we've done an initial reflow sr=attinasi

Comment on attachment 53446 [details] [diff] [review] diff -wu, only notify style set if we've done an initial reflow r=dbaron

Fix checked in. We might want to consider moving the BeginObservingDocument() call to _after_ the initial reflow, so we can squelch other notifications that won't do anything. I've put a comment to that effect in the code.

Marking verified in the Oct 22nd branch builds.