vold: Refactor Processkiller and add command to return users of a mount point

Signed-off-by: San Mehat <san@google.com>
diff --git a/ResponseCode.h b/ResponseCode.h
index 9d775f9..3508f81 100644
--- a/ResponseCode.h
+++ b/ResponseCode.h
@@ -23,8 +23,9 @@
     // before proceeding with a new command.
     static const int ActionInitiated  = 100;
 
-    static const int VolumeListResult = 110;
-    static const int AsecListResult   = 111;
+    static const int VolumeListResult         = 110;
+    static const int AsecListResult           = 111;
+    static const int StorageUsersListResult   = 112;
 
     // 200 series - Requested action has been successfully completed
     static const int CommandOkay              = 200;