Avoid calling overridable function from constructor

When a constructor calls an overridable function, it may allow an attacker to access the "this" reference prior to the object being fully initialized, which can in turn lead to a vulnerability.

Application -> getLocalPath
ProxyPanel -> get
AbortPanel -> get
RotatingBackgrounds -> makeEmpty

(Triggered by internal security audit and Fortify analysis.)

core/src/main/java/com/threerings/getdown/data/Application.java

@@ -36,7 +36,7 @@ import static java.nio.charset.StandardCharsets.UTF_8;
  * Parses and provide access to the information contained in the <code>getdown.txt</code>
  * configuration file.
  */
-public class Application
+public final class Application
 {
     /** The name of our configuration file. */
     public static final String CONFIG_FILE = "getdown.txt";

launcher/src/main/java/com/threerings/getdown/launcher/AbortPanel.java

@@ -28,7 +28,7 @@ import static com.threerings.getdown.Log.log;
 /**
  * Displays a confirmation that the user wants to abort installation.
  */
-public class AbortPanel extends JFrame
+public final class AbortPanel extends JFrame
     implements ActionListener
 {
     public AbortPanel (Getdown getdown, ResourceBundle msgs)

launcher/src/main/java/com/threerings/getdown/launcher/ProxyPanel.java

@@ -30,7 +30,7 @@ import static com.threerings.getdown.Log.log;
  * Displays an interface with which the user can configure their proxy
  * settings.
  */
-public class ProxyPanel extends JPanel
+public final class ProxyPanel extends JPanel
     implements ActionListener
 {
     public ProxyPanel (Getdown getdown, ResourceBundle msgs)

launcher/src/main/java/com/threerings/getdown/launcher/RotatingBackgrounds.java

@@ -10,7 +10,7 @@ import java.util.List;
 
 import static com.threerings.getdown.Log.log;
 
-public class RotatingBackgrounds
+public final class RotatingBackgrounds
 {
     public interface ImageLoader {
         /** Loads and returns the image with the supplied path. */

launcher/src/main/java/com/threerings/getdown/launcher/StatusPanel.java

@@ -36,7 +36,7 @@ import static com.threerings.getdown.Log.log;
 /**
  * Displays download and patching status.
  */
-public class StatusPanel extends JComponent
+public final class StatusPanel extends JComponent
     implements ImageObserver
 {
     public StatusPanel (ResourceBundle msgs)