Add a VpnManager.TYPE_VPN_OEM.

This needed for OEMs that have VPN types not supported by AOSP.

Bug: 171872481
Test: new test coverage in VpnTransportInfoTest
Change-Id: Ic7529bef7f12d2c74a3be5b1a4a2d54fb0d0bfac

core/java/android/net/VpnManager.java

@@ -85,6 +85,13 @@ public class VpnManager {
     @SystemApi(client = MODULE_LIBRARIES)
     public static final int TYPE_VPN_LEGACY = 3;
 
+    /**
+     * An VPN created by OEM code through other means than {@link VpnService} or {@link VpnManager}.
+     * @hide
+     */
+    @SystemApi(client = MODULE_LIBRARIES)
+    public static final int TYPE_VPN_OEM = 4;
+
     /**
      * Channel for VPN notifications.
      * @hide
@@ -92,7 +99,8 @@ public class VpnManager {
     public static final String NOTIFICATION_CHANNEL_VPN = "VPN";
 
     /** @hide */
-    @IntDef(value = {TYPE_VPN_NONE, TYPE_VPN_SERVICE, TYPE_VPN_PLATFORM, TYPE_VPN_LEGACY})
+    @IntDef(value = {TYPE_VPN_NONE, TYPE_VPN_SERVICE, TYPE_VPN_PLATFORM, TYPE_VPN_LEGACY,
+            TYPE_VPN_OEM})
     @Retention(RetentionPolicy.SOURCE)
     public @interface VpnType {}