Update HideOverlayWindowsTest to use new API

Bug: 171177581
Test: atest CtsWindowManagerDeviceTestCases:HideOverlayWindowsTest
Change-Id: Ib23360a38ca4775edb6bda9c5a9c953baee21950
diff --git a/tests/framework/base/windowmanager/src/android/server/wm/HideOverlayWindowsTest.java b/tests/framework/base/windowmanager/src/android/server/wm/HideOverlayWindowsTest.java
index 268b7ae..4a49d9a 100644
--- a/tests/framework/base/windowmanager/src/android/server/wm/HideOverlayWindowsTest.java
+++ b/tests/framework/base/windowmanager/src/android/server/wm/HideOverlayWindowsTest.java
@@ -193,15 +193,13 @@
             params.height = size.y / 3;
             params.gravity = TOP | LEFT;
             params.setTitle(windowName);
+            params.setSystemApplicationOverlay(
+                    getIntent().getBooleanExtra(SYSTEM_APPLICATION_OVERLAY_EXTRA, false));
 
             mTextView = new TextView(this);
             mTextView.setText(windowName + "   type=" + TYPE_APPLICATION_OVERLAY);
             mTextView.setBackgroundColor(Color.GREEN);
 
-            if (getIntent().getBooleanExtra(SYSTEM_APPLICATION_OVERLAY_EXTRA, false)) {
-                params.privateFlags |=
-                        WindowManager.LayoutParams.SYSTEM_FLAG_SYSTEM_APPLICATION_OVERLAY;
-            }
             getWindowManager().addView(mTextView, params);
         }