refactoring SizeEvent sending

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74096 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
refactoring SizeEvent sending

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74097 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775