Bug 96804

In bug 94982, the code for computeLogicalHeight was made const and put int a non-virtual function. This got rid of some hacks where we would store the old height, call computeLogicalHeight, then restore the old height. However, in the new code, it's hard to use computeLogicalHeight because it's not virtual so if you call it on a pointer and your pointer overrides updateLogicalHeight (e.g., it's an iframe), it'll do the wrong thing. See RenderBlock::computeBlockPreferredLogicalWidths for an example of where we would like to use childBox->computeLogicalHeight(..), but it crashes because sometimes childBox is a RenderView, which overrides updateLogicalHeight(). I think long term, we want to make computeLogicalHeight virtual and move code from the subclass updateLogicalHeight into it and then make updateLogicalHeight non-virtual.