Disallow screenshot on Wi-Fi QR code settings

- Add FLAG_SECURE to WifiDppConfiguratorActivity to avoid screenshot security issue

Bug: 249980936
Test: manual test
make RunSettingsRoboTests ROBOTEST_FILTER=WifiDppConfiguratorActivityTest

Change-Id: I5e62c2584122f79127ab505e8491565e163de296

tests/robotests/src/com/android/settings/wifi/dpp/WifiDppConfiguratorActivityTest.java

@@ -16,6 +16,10 @@
 
 package com.android.settings.wifi.dpp;
 
+import static android.view.WindowManager.LayoutParams.FLAG_SECURE;
+
+import static com.google.common.truth.Truth.assertThat;
+
 import static org.mockito.Mockito.doNothing;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.spy;
@@ -72,6 +76,12 @@ public class WifiDppConfiguratorActivityTest {
                 Robolectric.setupActivity(WifiDppConfiguratorActivity.class);
     }
 
+    @Test
+    public void launchActivity_shouldAddFlagSecure() {
+        assertThat(mActivity.getWindow().getAttributes().flags & FLAG_SECURE)
+                .isEqualTo(FLAG_SECURE);
+    }
+
     @Test
     public void handleIntent_isGuestUser_shouldFinish() {
         when(mUserManager.isGuestUser()).thenReturn(true);