adding ContentScaleFactor support to dc - defaulting to 1.0

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74282 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
formatting

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74283 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775