Fix broken HTML output. FlowDocument can't use save()/restore() when …

…changing styles, because a page-break will need a </g>, closing any style save()/restore(). Solution: not using that renderer state stack for FlowDocument apart from the onBeginPage callback. One rare case of the fix being now cleaner, more correct and faster at the same time :)

flow/printed/flow/document.d

@@ -495,15 +495,13 @@ private:
     {
         assert(_stateStack.length != 0);
         _stateStack ~= _stateStack[$-1];
-        _r.save();
     }
 
     // Pop (context information + fontSize).
     void popState()
     {
         assert(_stateStack.length >= 2);
         _stateStack = _stateStack[0..$-1];
-        _r.restore();
 
         // Apply former state to context
         updateRendererStateWithStyleState();