Protect VPN dialogs against overlay.

Bug: 130568701
Test: manual. After this, can't display on top of it
Change-Id: Ib032f800edb0416cc15f01a34954340d0d0ffa78
Merged-In: Ib032f800edb0416cc15f01a34954340d0d0ffa78
(cherry picked from commit 4e80dc2861614d25a1f957f50040a8cf04812d11)
(cherry picked from commit 016c72c8abfbae08eda269afb8923e8fc8a4ce44)
diff --git a/packages/VpnDialogs/AndroidManifest.xml b/packages/VpnDialogs/AndroidManifest.xml
index a3d27ce..60ed324 100644
--- a/packages/VpnDialogs/AndroidManifest.xml
+++ b/packages/VpnDialogs/AndroidManifest.xml
@@ -21,6 +21,7 @@
 
     <uses-permission android:name="android.permission.CONTROL_VPN" />
     <uses-permission android:name="android.permission.CONNECTIVITY_INTERNAL" />
+    <uses-permission android:name="android.permission.HIDE_NON_SYSTEM_OVERLAY_WINDOWS"/>
 
     <application android:label="VpnDialogs"
             android:allowBackup="false" >
diff --git a/packages/VpnDialogs/src/com/android/vpndialogs/ConfirmDialog.java b/packages/VpnDialogs/src/com/android/vpndialogs/ConfirmDialog.java
index 72ce9c4..0933974 100644
--- a/packages/VpnDialogs/src/com/android/vpndialogs/ConfirmDialog.java
+++ b/packages/VpnDialogs/src/com/android/vpndialogs/ConfirmDialog.java
@@ -16,6 +16,8 @@
 
 package com.android.vpndialogs;
 
+import static android.view.WindowManager.LayoutParams.PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS;
+
 import android.content.Context;
 import android.content.DialogInterface;
 import android.content.pm.PackageManager;
@@ -78,6 +80,7 @@
         setupAlert();
 
         getWindow().setCloseOnTouchOutside(false);
+        getWindow().addPrivateFlags(PRIVATE_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS);
         Button button = mAlert.getButton(DialogInterface.BUTTON_POSITIVE);
         button.setFilterTouchesWhenObscured(true);
     }