The size of HTML 'object' elements (and other replaced elements) may depend on the intrinsic size of the SVG it's embedding. If this is the case, then the 'object' element should resize as necessary when SVG content is unloaded (e.g. if someone clicks on a link in the SVG causing the SVG to be replaced by something else). Currently the 'object' element doesn't notice when its content is unloaded and thus it just keeps its old size.

Bug 1063073 fixed loading. That may have effectively fixed unloading for most cases, but we should probably also schedule a reflow in an nsSVGOuterSVGFrame::Destroy() implementation...except that nsIFrame::Destroy() is non-virtual.