Don't use ActivityManagerTestBase

Test: atest NotificationManagerTest
Bug: 145602966
Change-Id: I4785cf9b66fd480c7c7df65e0f4f7b205689ac73
diff --git a/tests/app/src/android/app/cts/NotificationManagerTest.java b/tests/app/src/android/app/cts/NotificationManagerTest.java
index fcd6a0a..ad455b6 100644
--- a/tests/app/src/android/app/cts/NotificationManagerTest.java
+++ b/tests/app/src/android/app/cts/NotificationManagerTest.java
@@ -100,7 +100,6 @@
 import android.provider.ContactsContract.Data;
 import android.provider.Settings;
 import android.provider.Telephony.Threads;
-import android.server.wm.ActivityManagerTestBase;
 import android.service.notification.Condition;
 import android.service.notification.NotificationListenerService;
 import android.service.notification.StatusBarNotification;
@@ -689,19 +688,12 @@
         mContext.unregisterReceiver(mBubbleBroadcastReceiver);
     }
 
-    private class HomeHelper extends ActivityManagerTestBase implements AutoCloseable {
-
-        HomeHelper() throws Exception {
-            setUp();
-        }
-
-        void goHome() {
-            launchHomeActivity();
-        }
-
-        @Override
-        public void close() throws Exception {
-            tearDown();
+    private static String goHome() {
+        try {
+            return SystemUtil.runShellCommand(InstrumentationRegistry.getInstrumentation(),
+                    "am start -a android.intent.action.MAIN -c android.intent.category.HOME");
+        } catch (IOException e) {
+            throw new RuntimeException(e);
         }
     }
 
@@ -2977,8 +2969,7 @@
             }
 
             // Make ourselves not foreground
-            HomeHelper homeHelper = new HomeHelper();
-            homeHelper.goHome();
+            goHome();
 
             // The notif should be allowed to update as a bubble
             a.sendBubble(4001, false /* autoExpand */);
@@ -3000,7 +2991,6 @@
             }
 
             cleanupSendBubbleActivity();
-            homeHelper.close();
         } finally {
             // turn off bubbles globally
             toggleBubbleSetting(false);