8051588: DataTransferer.getInstance throws ClassCastException in headless mode

Reviewed-by: serb, alexsch

src/share/classes/sun/awt/ComponentFactory.java

@@ -25,6 +25,8 @@
 
 package sun.awt;
 
+import sun.awt.datatransfer.DataTransferer;
+
 import java.awt.*;
 import java.awt.dnd.*;
 import java.awt.dnd.peer.DragSourceContextPeer;
@@ -93,4 +95,6 @@ public interface ComponentFactory {
     RobotPeer createRobot(Robot target, GraphicsDevice screen)
         throws AWTException, HeadlessException;
 
+    DataTransferer getDataTransferer();
+
 }

src/share/classes/sun/awt/HeadlessToolkit.java

@@ -25,6 +25,8 @@
 
 package sun.awt;
 
+import sun.awt.datatransfer.DataTransferer;
+
 import java.awt.*;
 import java.awt.dnd.*;
 import java.awt.dnd.peer.DragSourceContextPeer;
@@ -401,6 +403,11 @@ public class HeadlessToolkit extends Toolkit
         return null;
     }
 
+    @Override
+    public DataTransferer getDataTransferer() {
+        return null;
+    }
+
     @SuppressWarnings("deprecation")
     public FontMetrics getFontMetrics(Font font) {
         return tk.getFontMetrics(font);

src/share/classes/sun/awt/SunToolkit.java

@@ -205,8 +205,6 @@ public abstract class SunToolkit extends Toolkit
 
     public abstract boolean isTraySupported();
 
-    public abstract DataTransferer getDataTransferer();
-
     @SuppressWarnings("deprecation")
     public abstract FontPeer getFontPeer(String name, int style);
 

src/share/classes/sun/awt/datatransfer/DataTransferer.java

@@ -86,6 +86,7 @@ import java.util.Stack;
 import java.util.TreeMap;
 import java.util.TreeSet;
 
+import sun.awt.ComponentFactory;
 import sun.util.logging.PlatformLogger;
 
 import sun.awt.AppContext;
@@ -272,7 +273,7 @@ public abstract class DataTransferer {
      * instead, null will be returned.
      */
     public static synchronized DataTransferer getInstance() {
-        return ((SunToolkit) Toolkit.getDefaultToolkit()).getDataTransferer();
+        return ((ComponentFactory) Toolkit.getDefaultToolkit()).getDataTransferer();
     }
 
     /**