make it possible to cache the resulting pixmap with a metafile

If the metafile contains just one single bitmap, the drawing code
optimizes by just using that one bitmap. It (=the resulting pixmap
after scaling etc.) however has not been cached so far, which means
smoothscaling (to be done) would be quite slow with every paint.

Change-Id: I30950c55fbadfddedc7df31283c66ed064b1a1a6

svtools/source/graphic/grfmgr2.cxx

@@ -536,6 +536,7 @@ static BitmapEx checkMetadataBitmap( const BitmapEx& rBmpEx,
                                      const Size&     rRefSize,
                                      bool&           o_rbNonBitmapActionEncountered )
 {
+// NOTE: If you do changes in this function, change checkMetadataBitmap() in grfcache.cxx too.
     BitmapEx aBmpEx;
     if( rSrcSize == Size())
         rSrcSize = rBmpEx.GetSizePixel();
@@ -609,6 +610,9 @@ sal_Bool GraphicManager::ImplCreateOutput( OutputDevice* pOut,
         const MapMode rPrefMapMode( rMtf.GetPrefMapMode() );
         const Size rSizePix( pOut->LogicToPixel( aNewSize, rPrefMapMode ) );
 
+// NOTE: If you do changes in this function, check GraphicDisplayCacheEntry::IsCacheableAsBitmap
+// in grfcache.cxx too.
+
         // Determine whether the metafile basically displays
         // a single bitmap (in which case that bitmap is simply used directly
         // instead of playing the metafile). Note that