1433362 - Avoid removing each observers for nsRefreshDriver when we destroy the root document

Status: NEW

(Core :: Layout, enhancement, P3)

Description

[Hiroyuki Ikezoe (:hiro)]

As Brian noted in bug 1415780 comment 47, when we destroy a document, we call RemoveStyleFlushObserver() [1] and also other observers for nsRefreshDriver.  In the case we destroy the root document, it will end up O(N^2) cost there.  We should avoid it somehow.

[1] https://hg.mozilla.org/mozilla-central/file/723b25eb3dd8/layout/base/nsRefreshDriver.h#l183

Comment 1

[Hiroyuki Ikezoe (:hiro)]

FWIW, I did push a try with removing all observers in descendants;

https://treeherder.mozilla.org/#/jobs?repo=try&revision=50f87640b253417951deed58a699d63fb18f39eb

Is seems there are some test cases that we shouldn't remove descendant observers for reflows?

https://treeherder.mozilla.org/#/jobs?repo=try&revision=50f87640b253417951deed58a699d63fb18f39eb&selectedJob=158656966

Comment 2

[Jet Villegas (inactive)]

[ Triage 2017/02/20: P3 ]