Show ProgressMonitorJobsDialog after delay in ProgressManager.run

Even for the backwards compatible mode (when the runnable is not forked
or non-cancelable).
This commit improves upon ccafe58 by
letting the dialog pop up (after a delay) if the preferences "Always run
in background" is set to false. When the preference is set to true, no
progress dialog will ever pop up.

Author: fedejeanne

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/progress/ProgressManager.java

@@ -971,8 +971,9 @@ public void run(boolean fork, boolean cancelable, IRunnableWithProgress runnable
 			// Backward compatible code.
 			final ProgressMonitorJobsDialog dialog = new ProgressMonitorJobsDialog(
 					ProgressManagerUtil.getDefaultParent());
-			if (shouldRunInBackground()) {
-				dialog.setOpenOnRun(false);
+			dialog.setOpenOnRun(false);
+			if (!shouldRunInBackground()) {
+				scheduleProgressMonitorJob(dialog);
 			}
 			dialog.run(fork, cancelable, runnable);
 			return;