Try make this more robust in slow environments

...where the previous .uno:PrintPreview request has not yet been processed and
xRoot/oObj would still be null.  Hopefully, it does not introduce infinite
loops, though.

Change-Id: Ie79e0b0a3185528ab4036ed7a33de81117c02c83

qadevOOo/tests/java/mod/_sc/ScAccessiblePageHeader.java

@@ -90,8 +90,6 @@ public class ScAccessiblePageHeader extends TestCase {
     protected TestEnvironment createTestEnvironment(
         TestParameters Param, PrintWriter log) {
 
-        XInterface oObj = null;
-
         // inserting some content to have non-empty page preview
         XCell xCell = null;
         try {
@@ -137,20 +135,28 @@ public class ScAccessiblePageHeader extends TestCase {
             throw new StatusException(Status.failed("Couldn't change mode"));
         }
 
-        try {
-            Thread.sleep(500);
-        } catch (InterruptedException ex) {}
-
         AccessibilityTools at = new AccessibilityTools();
 
+        XInterface oObj = null;
+        for (;;) {
+            try {
+                Thread.sleep(500);
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
             XWindow xWindow = AccessibilityTools.getCurrentWindow( (XMultiServiceFactory) Param.getMSF(), aModel);
             XAccessible xRoot = AccessibilityTools.getAccessibleObject(xWindow);
-
+            if (xRoot != null) {
                 oObj = AccessibilityTools.getAccessibleObjectForRole
                     (xRoot, AccessibleRole.HEADER, "");
-
+                if (oObj != null) {
                     log.println("ImplementationName " + utils.getImplName(oObj));
                     AccessibilityTools.printAccessibleTree(log, xRoot, Param.getBool(util.PropertyName.DEBUG_IS_ACTIVE));
+                    break;
+                }
+            }
+            log.println("No HEADER found yet, retrying");
+        }
 
         TestEnvironment tEnv = new TestEnvironment(oObj);