Add @IntDef for backup transport flags

This addresses the feedback from API council in b/183938013.

Fixes: 183938013
Test: m -j
Change-Id: I3ebf24053ce1ec6cdda60e4dc25ed92641f087fa

core/java/android/app/backup/BackupAgent.java

@@ -16,6 +16,7 @@
 
 package android.app.backup;
 
+import android.annotation.IntDef;
 import android.annotation.Nullable;
 import android.app.IBackupAgent;
 import android.app.QueuedWork;
@@ -48,6 +49,8 @@ import org.xmlpull.v1.XmlPullParserException;
 import java.io.File;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -188,6 +191,15 @@ public abstract class BackupAgent extends ContextWrapper {
      */
     public static final int FLAG_FAKE_CLIENT_SIDE_ENCRYPTION_ENABLED = 1 << 31;
 
+    /** @hide */
+    @Retention(RetentionPolicy.SOURCE)
+    @IntDef(flag = true, value = {
+            FLAG_CLIENT_SIDE_ENCRYPTION_ENABLED,
+            FLAG_DEVICE_TO_DEVICE_TRANSFER,
+            FLAG_FAKE_CLIENT_SIDE_ENCRYPTION_ENABLED
+    })
+    public @interface BackupTransportFlags {}
+
     Handler mHandler = null;
 
     @Nullable private UserHandle mUser;

core/java/android/app/backup/RestoreSet.java

@@ -18,6 +18,7 @@ package android.app.backup;
 
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
+import android.app.backup.BackupAgent.BackupTransportFlags;
 import android.os.Parcel;
 import android.os.Parcelable;
 
@@ -54,6 +55,7 @@ public class RestoreSet implements Parcelable {
      * Properties of the {@link BackupTransport} transport that was used to obtain the data in
      * this restore set.
      */
+    @BackupTransportFlags
     public final int backupTransportFlags;
 
     /**
@@ -87,7 +89,7 @@ public class RestoreSet implements Parcelable {
      *                             flag values.
      */
     public RestoreSet(@Nullable String name, @Nullable String device, long token,
-            int backupTransportFlags) {
+            @BackupTransportFlags int backupTransportFlags) {
         this.name = name;
         this.device = device;
         this.token = token;