8291456: com/sun/jdi/ClassUnloadEventTest.java failed with: Wrong number of class unload events: expected 10 got 4

Backport-of: c5e0464098f8f7cd9c568c7b1c3a06139453eaab

Author: adinn

test/jdk/com/sun/jdi/ClassUnloadEventTest.java

@@ -117,13 +117,8 @@ private static void runDebuggee() {
         // Trigger class unloading
         ClassUnloadCommon.triggerUnloading();
 
-        // Do a short delay to make sure all ClassUnloadEvents have been sent
-        // before VMDeathEvent is generated.
-        try {
-            Thread.sleep(5000);
-        } catch (InterruptedException e) {
-        }
-
+        // We rely on JVMTI to post all pending ObjectFree events at VM shutdown.
+        // It will trigger the JDWP agent to synthesize expected ClassUnloadEvents events.
         System.out.println("Exiting debuggee");
     }