fdo#58995 fix focus gain/lost events dropping on JDK 1.7

With JDK upgrade to 1.7.x focus gain/lost events were dropped and thus not
discoverable by AT tools.

The problem has nothing to do with different packaging of JAB (2.0.3 is
included with JDK 1.7u6 and higher).

The reason for the event droping was a new check in
DefaultKeyboardFocusManager.java that was introduced in JDK 1.7.x:

@@ -294,18 +271,10 @@ public class DefaultKeyboardFocusManager
        extends KeyboardFocusManager {

-      if (!(newFocusedWindow.isFocusableWindow()
-               && newFocusedWindow.isVisible()
-               && newFocusedWindow.isDisplayable()))
-         {
-             // we can not accept focus on such window, so reject it.
-             restoreFocus(we);
-             break;
-         }

With this check in place it is assumed that Component.isDisplayable() must
return true, for event to be dispatched. But particularly
`Dialog.isDisplayable()` didn't and thus all tab key events (focus traversal)
were dropped.

Many thanks to Jamie and Stuart for helping out with reproducing and tracking that down!

Change-Id: I4876773199ca06a6e73213401692e8275a1f3b22

accessibility/bridge/org/openoffice/java/accessibility/Dialog.java

@@ -123,6 +123,27 @@ public class Dialog extends java.awt.Dialog implements javax.accessibility.Acces
         return visible;
     }
 
+    /**
+     * Determines whether this component is displayable. A component is
+     * displayable when it is connected to a native screen resource.
+     * <p>
+     * A component is made displayable either when it is added to
+     * a displayable containment hierarchy or when its containment
+     * hierarchy is made displayable.
+     * A containment hierarchy is made displayable when its ancestor
+     * window is either packed or made visible.
+     * <p>
+     * A component is made undisplayable either when it is removed from
+     * a displayable containment hierarchy or when its containment hierarchy
+     * is made undisplayable.  A containment hierarchy is made
+     * undisplayable when its ancestor window is disposed.
+     *
+     * @return <code>true</code> if the component is displayable
+     */
+    public boolean isDisplayable() {
+        return true;
+    }
+
     /**
     * Shows or hides this component depending on the value of parameter
     * <code>b</code>.