using common GetContentScaleFactor throughout part 1

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74255 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
using common GetContentScaleFactor throughout part 2/2

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74256 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
fixing iPhone build

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74257 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775