Expose network scoring APIs to /system apps.

Ideally, we'd only expose the methods that we intend unbundled apps to
call (e.g. not NetworkScoreManager#setActiveScorer, which should only
be called by Settings), but this isn't harmful in terms of permissions
as the APIs still check security appropriately.

Bug: 15833200
Change-Id: I2047515b41c8be0cf7cb51dd495fe72309c05f68
diff --git a/core/java/android/net/NetworkScoreManager.java b/core/java/android/net/NetworkScoreManager.java
index c599dfc..b497c6e 100644
--- a/core/java/android/net/NetworkScoreManager.java
+++ b/core/java/android/net/NetworkScoreManager.java
@@ -18,6 +18,7 @@
 
 import android.annotation.SdkConstant;
 import android.annotation.SdkConstant.SdkConstantType;
+import android.annotation.SystemApi;
 import android.content.Context;
 import android.content.Intent;
 import android.net.NetworkScorerAppManager.NetworkScorerAppData;
@@ -52,6 +53,7 @@
  *
  * @hide
  */
+@SystemApi
 public class NetworkScoreManager {
     /**
      * Activity action: ask the user to change the active network scorer. This will show a dialog