Created attachment 564018 [details] testcase ###!!! ASSERTION: aPrevFrame must be the last continuation in its chain!: '!aPrevFrame || (!aPrevFrame->GetNextContinuation() || IS_TRUE_OVERFLOW_CONTAINER(aPrevFrame->GetNextContinuation())) && !IS_TRUE_OVERFLOW_CONTAINER(aPrevFrame)', file layout/base/nsFrameManager.cpp, line 497
Created attachment 565635 [details] [diff] [review] Patch (v1) I don't think that the assertion actually makes any sense for absolute frames.
Because we're not appending a frame after aPrevFrame. Or at least, it should be possible to append an absolute frame in that case.
aPrevFrame would be the previous abs-pos frame.
(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #6) > aPrevFrame would be the previous abs-pos frame. But still, does the assertion make sense? We don't require abs-pos frames to be overflow containers, right?
They can't be true overflow containers, actually. See the definition of IS_TRUE_OVERFLOW_CONTAINER. I think probably instead of checking IS_TRUE_OVERFLOW_CONTAINER we should just check for the NS_FRAME_IS_OVERFLOW_CONTAINER state bit.
Created attachment 585539 [details] [diff] [review] Patch (v2)
Try run for 689ef914ab82 is complete. Detailed breakdown of the results available here: https://tbpl.mozilla.org/?tree=Try&rev=689ef914ab82 Results (out of 208 total builds): exception: 3 success: 181 warnings: 23 failure: 1 Builds (or logs if builds failed) available at: http://email@example.com