The patch in http://bugs.webkit.org/show_bug.cgi?id=15569 introduced JS_EXPORT to export public API without defs file entries in r28097. It was backed out in r28100 because we couldn't figure out how to define JS_BUILDING_JS in the windows build system (which is required by MSVC to decide between dllimport and dllexport). Once this is done, r28100 should be re-introduced and redundant entries removed from the Win defs file.
This is fixed in r42680 for the Windows build. The change requires proper definition of a BUILDING_{projectname} preprocessor def. We have this defined in win/tools/vsprops/common.vsprops.
There’s still a comment with this bug number in it in JSBase.h. What should we do about that?
I'll remove the comment.