Revert "CppunitTest_tiledrendering: disable SwVirtFlyDrawObj assert for now"

This is a real problem, which is fixed in a following commit -- tiled
rendering does not currently set the viewport at all, which can result
in an empty (or otherwise incorrect viewport), so this assert is definitely
valid.

This reverts commit fb0b42b8.

sw/inc/viewsh.hxx

@@ -571,7 +571,6 @@ public:
     bool IsShowHeaderFooterSeparator( FrameControlType eControl ) { return (eControl == Header)? mbShowHeaderSeparator: mbShowFooterSeparator; }
     virtual void SetShowHeaderFooterSeparator( FrameControlType eControl, bool bShow ) { if ( eControl == Header ) mbShowHeaderSeparator = bShow; else mbShowFooterSeparator = bShow; }
     bool IsSelectAll() { return mbSelectAll; }
-    bool IsTiledRendering() { return mbTiledRendering; }
 };
 
 // manages global ShellPointer

sw/source/core/draw/dflyobj.cxx

@@ -469,9 +469,7 @@ void SwVirtFlyDrawObj::wrap_DoPaintObject(
             // if there's no viewport set, all fly-frames will be painted,
             // which is slow, wastes memory, and can cause other trouble.
             (void) rViewInformation; // suppress "unused parameter" warning
-            if (!pShell->IsTiledRendering())
-                // FIXME is it OK to have no viewport during tiled rendering?
-                assert(!rViewInformation.getViewport().isEmpty());
+            assert(!rViewInformation.getViewport().isEmpty());
             if ( !pFlyFrm->IsFlyInCntFrm() )
             {
                 // it is also necessary to restore the VCL MapMode from ViewInformation since e.g.