fixes a crasher when reframing fixed-pos frames.
This change adds an assertion in ConstructHTMLFrame that InitAndRestoreFrame
should succeed (unless it returns NS_ERROR_FRAME_REPLACED). This is an interim
change; eventually we want to bail out on errors, but there may be frame impls
that return errors in non-error conditions from Init() (eg nsFrameSetFrame did
that) and we're a little close to freeze.
Bug 202506, r=rbs, sr=roc+moz
git-svn-id: svn://10.0.0.236/trunk@141552 18797224-902f-48f8-a5cc-f745e15eee43
