Add SYSTEM_APPLICATION_OVERLAY

.. which allows the holder to create privileged application overlays
that won't be hidden by Window#hideOverlayWindows

Bug: 159616727
Bug: 171177581
Test: atest CtsWindowManagerDeviceTestCases:HideOverlayWindowsTest
Change-Id: I1a8c08047ca51b12067fa68bea61843013940643
diff --git a/packages/Shell/AndroidManifest.xml b/packages/Shell/AndroidManifest.xml
index 0a43014..0fd9e21 100644
--- a/packages/Shell/AndroidManifest.xml
+++ b/packages/Shell/AndroidManifest.xml
@@ -369,8 +369,9 @@
     <!-- Permissions required for CTS tests to close system dialogs -->
     <uses-permission android:name="android.permission.BROADCAST_CLOSE_SYSTEM_DIALOGS" />
 
-    <!-- Permission required for CTS test - HideOverlayWindowsTest -->
+    <!-- Permissions required for CTS test - HideOverlayWindowsTest -->
     <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
+    <uses-permission android:name="android.permission.SYSTEM_APPLICATION_OVERLAY"/>
 
     <!-- Permission required for CTS test - CtsHdmiCecHostTestCases -->
     <uses-permission android:name="android.permission.HDMI_CEC" />