ADDITIONAL SYSTEM INFORMATION :
All OS

A DESCRIPTION OF THE PROBLEM :
"=" is missing in following line of isComplexCharCode().
modules/javafx.graphics/src/main/java/com/sun/javafx/text/ScriptMapper.java

    else if (code < 0x11ff) { // U+1100 - U+11FF Old Hangul
        return true;
    }

----> Fix

    else if (code <= 0x11ff) { // U+1100 - U+11FF Old Hangul
        return true;
    }

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Nothing specially.
Attached test case is displayed correctly in both case before/after modify (code <= 0x11ff).

If you would like to check modify is correct, Please run jdb.
# LANG=C ./jdk/build/linux-x86_64-normal-server-release/images/jdk/bin/jdb U_11FF_Test
[#jdb] stop in com.sun.javafx.text.PrismTextLayout.shape
[#jdb] run
[#jdb] print layout

OK : layout = PangoGlyphLayout (Linux), DWGlyphLayout (Windows)
NG : layout = null

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JavaFX Application Thread[1] print layout
 layout = "com.sun.javafx.font.freetype.PangoGlyphLayout@2c8a795"

ACTUAL -
JavaFX Application Thread[1] print layout
 layout = null

---------- BEGIN SOURCE ----------
import javafx.application.Application;
import static javafx.application.Application.launch;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class U_11FF_Test extends Application {

    public void start(Stage stage) {
        final String family = "Unifont";
        // download GNU Unifont and install
        // http://www.unifoundry.com/unifont.html
        // http://unifoundry.com/pub/unifont-11.0.01/font-builds/unifont-11.0.01.ttf

        Font font = Font.font(family, 48.0);
        if (font == null || !family.equals(font.getFamily())) {
            System.err.println("# You need to install font "+family);
            System.exit(0);
        }

        stage.setWidth(140);
        stage.setHeight(160);
        Group g = new Group();
        final Scene scene = new Scene(new Group());
        VBox box = new VBox();
        ((Group)scene.getRoot()).getChildren().add(box);
        stage.setScene(scene);

        Text txt = new Text("\u11ff"); // U+11FF (Old Hangul)
        txt.setFont(font);
        box.getChildren().add(txt);

        stage.show();
    }
}
---------- END SOURCE ----------

FREQUENCY : always