Define initial trust agent API

Adds the minimal API needed to define a useful trust agent.

Bug: 13723878
Change-Id: Ib24440bab7b16d0b656bde8b059e7d42cab2c7dc
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 2168bd1..2e0ac08 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -2548,6 +2548,14 @@
         android:description="@string/permdesc_control_keyguard" />
 
     <!-- Must be required by an {@link
+         android.service.trust.TrustAgentService},
+         to ensure that only the system can bind to it. -->
+    <permission android:name="android.permission.BIND_TRUST_AGENT_SERVICE"
+                android:protectionLevel="signature"
+                android:label="@string/permlab_bind_trust_agent_service"
+                android:description="@string/permdesc_bind_trust_agent_service" />
+
+    <!-- Must be required by an {@link
          android.service.notification.NotificationListenerService},
          to ensure that only the system can bind to it. -->
     <permission android:name="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE"