Prevent overlay drawing on top of Bluetooth activity dialog

Bug: 168504491
Change-Id: I04ebe580db2b299af2bd5e44e0b0f20bd42f8535
(cherry picked from commit 4f7edf692f4e8a10521379aaae8c1d52ab275d72)
diff --git a/src/com/android/settings/bluetooth/BluetoothPermissionActivity.java b/src/com/android/settings/bluetooth/BluetoothPermissionActivity.java
index 4dd9a40..be383dc 100644
--- a/src/com/android/settings/bluetooth/BluetoothPermissionActivity.java
+++ b/src/com/android/settings/bluetooth/BluetoothPermissionActivity.java
@@ -34,6 +34,8 @@
 import com.android.internal.app.AlertController;
 import com.android.settings.R;
 
+import static android.view.WindowManager.LayoutParams.SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
+
 /**
  * BluetoothPermissionActivity shows a dialog for accepting incoming
  * profile connection request from untrusted devices.
@@ -76,6 +78,7 @@
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
+        getWindow().addPrivateFlags(SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
         Intent i = getIntent();
         String action = i.getAction();
         if (!action.equals(BluetoothDevice.ACTION_CONNECTION_ACCESS_REQUEST)) {