Add content description to VPN

Went missing oops

Test: turn on talkback
Change-Id: I600fe74900f65d6f6941d7b45390ea8bf92acf24
Fixes: 117795996
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarSignalPolicy.java b/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarSignalPolicy.java
index 384a6e7..4c24a21 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarSignalPolicy.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBarSignalPolicy.java
@@ -101,7 +101,8 @@
         boolean vpnVisible = mSecurityController.isVpnEnabled();
         int vpnIconId = currentVpnIconId(mSecurityController.isVpnBranded());
 
-        mIconController.setIcon(mSlotVpn, vpnIconId, null);
+        mIconController.setIcon(mSlotVpn, vpnIconId,
+                mContext.getResources().getString(R.string.accessibility_vpn_on));
         mIconController.setIconVisibility(mSlotVpn, vpnVisible);
     }