Update printer metrics after resolution change.

[ChangeLog][QtPrintSupport] Fixed QPrinter::{width,height} return values
when the resolution is changed in the print dialog.

Task-number: QTBUG-43124
Change-Id: Ib805907affed4b1ffb48e6b1ff89f7a79ab3e329
Reviewed-by: Andy Shaw <andy.shaw@digia.com>

src/printsupport/kernel/qprintengine_win.cpp

@@ -931,6 +931,8 @@ void QWin32PrintEnginePrivate::initHDC()
     default:
         break;
     }
+
+    updateMetrics();
 }
 
 void QWin32PrintEnginePrivate::release()