User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 (Beta/Release) Build ID: 20131018030206 Steps to reproduce: 1. Open the test.html file 2. Click the "+" button Actual results: The bottom of the scroll bar appeared in the step 2. Expected results: Scroll bar is always hidden. Regression window(m-c) Good: http://hg.mozilla.org/mozilla-central/rev/423b9c30c73d Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131017030201 Bad: http://hg.mozilla.org/mozilla-central/rev/4e7d1e2c93a6 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131018030206 Sorry for my bad English.

Regression window(m-i) Good: http://hg.mozilla.org/integration/mozilla-inbound/rev/9c8ab7e9ae41 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131017025216 Bad: http://hg.mozilla.org/integration/mozilla-inbound/rev/45d9e6cd3473 Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131017030414 Pushlog: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=9c8ab7e9ae41&tochange=45d9e6cd3473 Suspected: Bug 926706

roc - what's your read on this? I can't tell whether a large segment of the web would be impacted.

I'm not sure but we should definitely fix it before release.

Comment on attachment 820308 [details] [diff] [review] fix It looks like IsCollapsed() is only relevant in the XUL case at least.

I don't think this is ready to land.

Whole push backed out since not clear what caused the reftest failures: https://tbpl.mozilla.org/?tree=Mozilla-Inbound&rev=ffd9c7bbd2fe&jobname=reftest remote: https://hg.mozilla.org/integration/mozilla-inbound/rev/69d9f136cf26 remote: https://hg.mozilla.org/integration/mozilla-inbound/rev/b71812b077de

Oops. (In reply to Timothy Nikkel (:tn) from comment #5) > It looks like IsCollapsed() is only relevant in the XUL case at least. What's wrong with just calling it?

BTW this caused reftest failure: https://tbpl.mozilla.org/php/getParsedLog.php?id=29555168&tree=Mozilla-Inbound&full=1#error0 I plan to just fuzz the test on Mac. I think this is a longstanding issue where the edges of invalidated areas are sometimes off by 1/255 on Mac.

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #9) > Oops. > > (In reply to Timothy Nikkel (:tn) from comment #5) > > It looks like IsCollapsed() is only relevant in the XUL case at least. > > What's wrong with just calling it? You can call it, but it looks like it should only be used here in the XUL collapsed sense, and not the table part collapsed sense.

http://www.mozilla.org/en-US/firefox/community/ page is also affected

This code blocks comes from bug 524925 where it looks like it as pulled from nsBox::SyncLayout. And that chunk of code in nsBox::SyncLayout is only executed on frames for which ComputesOwnOverflowArea() is false. And it seems that only some XUL frames have ComputesOwnOverflowArea() return false.

Looks good to me. Build ID: 20131028040205

Tested http://www.mozilla.org/en-US/contribute/ and the testcase.

Comment on attachment 822364 [details] [diff] [review] fix v2 [Approval Request Comment] Bug caused by (feature/regressing bug #): User impact if declined: column flicker - bug 917060 Testing completed (on m-c, etc.): on m-c since 2013-10-26, also in Aurora(27) Risk to taking this patch (and alternatives if risky): low risk String or IDL/UUID changes made by this patch: none Landing bug 926706 and bug 928607 on Beta(26) to fix/wallpaper bug 917060 should be straightforward and lower risk than backing out what caused that bug.

changing 26 to 'affected' since we'll be landing this there and it shouldn't state 'unaffected'