This changed after the OOUI font-size change. Also reduce
the preview height which is measure in em's so that it is
closer to its original pixel value.
Also fix line height for error messages.
Change-Id: I3537d33dc1889e0154f4574bb33b22b3c006fe9c
The chemical and mathematical formula inspectors and dialogs
have a lot of similar functionality, and the common parts are
now moved to the common MWLatex class.
MWMath* classes now inherit from MWLatex*, and so do
the new MWChem* classes.
Bug: T153365
Change-Id: I4452ceca55197fda5f1e1293a5741c6f5fb7c245