Prevent overlays on Telephony settings screen.

Ensure only system overlays are allowed on telephony settings screens.

Flag: NONE Security fix
Bug: 335387175
Test: Manually launched activities to verify no overlays are possible.
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:46e18ac57da3ac50271fc2be5b20bd7799637eae)
Merged-In: I953667309753ff6fc966956e246512de97ad8638
Change-Id: I953667309753ff6fc966956e246512de97ad8638
diff --git a/src/com/android/phone/CallFeaturesSetting.java b/src/com/android/phone/CallFeaturesSetting.java
index 1c55256..bec2a81 100644
--- a/src/com/android/phone/CallFeaturesSetting.java
+++ b/src/com/android/phone/CallFeaturesSetting.java
@@ -257,6 +257,10 @@
         super.onCreate(icicle);
         if (DBG) log("onCreate: Intent is " + getIntent());
 
+        getWindow().addSystemFlags(
+                android.view.WindowManager.LayoutParams
+                        .SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
+
         // Make sure we are running as an admin user.
         UserManager userManager = (UserManager) getSystemService(Context.USER_SERVICE);
         if (!userManager.isAdminUser()) {