Loading the testcase triggers a bunch of assertions related to NS_UNCONSTRAINEDSIZE: ###!!! ASSERTION: This shouldn't be called anymore: 'Not Reached', file mozilla/layout/generic/nsLineLayout.cpp, line 2474 ###!!! ASSERTION: computed width should always be computed: 'computedSize.width != NS_INTRINSICSIZE', file mozilla/layout/xul/base/src/nsBoxFrame.cpp, line 707 ###!!! ASSERTION: math on NS_UNCONSTRAINEDSIZE: 'NS_UNCONSTRAINEDSIZE != aState.mReflowState.mComputedBorderPadding.left && NS_UNCONSTRAINEDSIZE != aState.mReflowState.ComputedWidth()', file mozilla/layout/generic/nsBlockFrame.cpp, line 1453 ###!!! ASSERTION: no unconstrained widths should be present anymore: 'NS_UNCONSTRAINEDSIZE != aReflowState.ComputedWidth()', file mozilla/layout/generic/nsBlockReflowState.cpp, line 110 ###!!! ASSERTION: shouldn't have unconstrained widths anymore: 'NS_UNCONSTRAINEDSIZE != aReflowState.availableWidth', file mozilla/layout/generic/nsLineLayout.cpp, line 1134 ###!!! ASSERTION: shouldn't have unconstrained widths anymore: 'psd->mRightEdge != NS_UNCONSTRAINEDSIZE', file mozilla/layout/generic/nsLineLayout.cpp, line 823 ###!!! ASSERTION: shouldn't use unconstrained widths anymore: '(mFrameType == NS_CSS_FRAME_TYPE_INLINE && !frame->IsFrameOfType(nsIFrame::eReplaced)) || frame->GetType() == nsGkAtoms::textFrame || mComputedWidth != NS_UNCONSTRAINEDSIZE', file mozilla/layout/generic/nsHTMLReflowState.cpp, line 295 ###!!! ASSERTION: shouldn't use unconstrained widths anymore: 'availableWidth != NS_UNCONSTRAINEDSIZE', file mozilla/layout/generic/nsHTMLReflowState.cpp, line 274 ###!!! ASSERTION: unconstrained widths no longer supported: 'aContainingBlockWidth != NS_UNCONSTRAINEDSIZE', file mozilla/layout/base/nsLayoutUtils.cpp, line 1601

Jesse, are all of those assertions related to each other? Or shall we better separate them in own bugs?

I'm assuming they're all related. They're pretty much all about widths being wrong, and most of them involve NS_UNCONSTRAINEDSIZE.

I'm getting these assertions with layout/base/crashtests/265986-1.html as well

WFM with this testcase. I filed bug 512405 for comment 3.

Crashtest: http://hg.mozilla.org/mozilla-central/rev/b64a7e4a35e2