javafx.media classes directly reference platform classes that are excluded

The following shared code in javafx.media directly references a platform-specific class, which is available at compile-time, but then is excluded from the delivered module by the build. We do this for other platform-specific classes, but they are all loaded by reflection.

com/sun/media/jfxmediaimpl/platform/PlatformManager.java

        if (HostUtils.isIOS() && isPlatformEnabled("IOSPlatform")) {
            platty = IOSPlatform.getPlatformInstance();
            if (null != platty) {
                platforms.add(platty);
            }
        }

See JDK-8211887 for at least one problem that this causes.