Opt-out for always-on VPN: rename API.

Rename the opt-out flag in AndroidManifest to
SERVICE_META_DATA_SUPPORTS_ALWAYS_ON
as directed by the API Council.

Bug: 64331776
Bug: 36650087
Test: runtest --path java/com/android/server/connectivity/VpnTest.java
Change-Id: I24326fad7a89083a2409134640bda81ee0359d08
diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index d8da8c5..6f9484c 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -3938,7 +3938,7 @@
      *         {@link android.Manifest.permission#BIND_VPN_SERVICE};</li>
      *     <li>target {@link android.os.Build.VERSION_CODES#N API 24} or above; and</li>
      *     <li><i>not</i> explicitly opt out of the feature through
-     *         {@link android.net.VpnService#METADATA_SUPPORTS_ALWAYS_ON}.</li>
+     *         {@link android.net.VpnService#SERVICE_META_DATA_SUPPORTS_ALWAYS_ON}.</li>
      * </ul>
      * The call will fail if called with the package name of an unsupported VPN app.
      *
diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index 48123fe..744ee8e 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -840,8 +840,8 @@
      * In order to support the always-on feature, an app has to
      * <ul>
      *     <li>target {@link VERSION_CODES#N API 24} or above, and
-     *     <li>not opt out through the {@link VpnService#METADATA_SUPPORTS_ALWAYS_ON} meta-data
-     *         field.
+     *     <li>not opt out through the {@link VpnService#SERVICE_META_DATA_SUPPORTS_ALWAYS_ON}
+     *         meta-data field.
      * </ul>
      *
      * @param userId The identifier of the user for whom the VPN app is installed.
diff --git a/core/java/android/net/VpnService.java b/core/java/android/net/VpnService.java
index 7fb0c47..185b181 100644
--- a/core/java/android/net/VpnService.java
+++ b/core/java/android/net/VpnService.java
@@ -152,9 +152,10 @@
      * </service>
      * } </pre>
      *
-     * <p>This meta-data field defaults to {@code true} if absent.
+     * <p>This meta-data field defaults to {@code true} if absent. It will only have effect on
+     * {@link android.os.Build.VERSION_CODES#O_MR1} or higher.
      */
-    public static final String METADATA_SUPPORTS_ALWAYS_ON =
+    public static final String SERVICE_META_DATA_SUPPORTS_ALWAYS_ON =
             "android.net.VpnService.SUPPORTS_ALWAYS_ON";
 
     /**