Now EFL port is only using a Page in RenderTheme::themeForPage. I don't sure yet why EFL port needs to use it though, it seems to me that EFL port can has different themes per a Page. I don't know if we should support this feature.
Closing this bug because the EFL port has been removed from trunk.
If you feel this bug applies to a different upstream WebKit port and was closed in error, please either update the title and reopen the bug, or leave a comment to request this.