My local DEBUG m-c fails to build. I suspect the problem might be hidden on tbpl because of unified builds chunking or something... (fwiw, adding an #include nsLayoutUtils.h fixed it) widget/cocoa/nsChildView.mm:405:44: error: use of undeclared identifier 'nsLayoutUtils' nsCOMPtr<nsIContent> targetContent = nsLayoutUtils::FindContentFor(mFrameMetrics.GetScrollId());
Looks like that was added in http://hg.mozilla.org/mozilla-central/rev/2dd00ac41fbe (bug 944938)
In my build, nsChildView.mm includes nsLayoutUtils.h through this include chain: nsChildView.mm -> nsAccessibilityService.h -> SelectionManager.h -> nsIFrame.h -> nsLayoutUtils.h Are you building with --disable-accessibility?
(In reply to Markus Stange [:mstange] from comment #2) > Are you building with --disable-accessibility? Correct. (sorry for failing to mention it's a non-default mozconfig)