Multi-user - wallpaper service

- Allow each user to have their own wallpaper (live or static).
- Migrate old wallpaper on upgrade.
- Update SystemBackupAgent to backup/restore from primary user's
  new wallpaper directory.

Reduce dependency on Binder.getOrigCallingUser() by passing the
userId for bindService.

Change-Id: I19c8c3296d3d2efa7f28f951d4b84407489e2166
diff --git a/test-runner/src/android/test/mock/MockContext.java b/test-runner/src/android/test/mock/MockContext.java
index 0b4fc51..674c0b7 100644
--- a/test-runner/src/android/test/mock/MockContext.java
+++ b/test-runner/src/android/test/mock/MockContext.java
@@ -333,6 +333,12 @@
         throw new UnsupportedOperationException();
     }
 
+    /** @hide */
+    @Override
+    public boolean bindService(Intent service, ServiceConnection conn, int flags, int userId) {
+        throw new UnsupportedOperationException();
+    }
+
     @Override
     public void unbindService(ServiceConnection conn) {
         throw new UnsupportedOperationException();