Hello Prem,
I have implemented this feature and it will be available in version 3.0.0 when it is released. You can grab a beta build now at
https://bugs.launchpad.net/autosizer/+bug/1266359, see the packages attached in the comments.
To get the behaviour you want open the preferences dialog and uncheck "size on content" and check "size on focus".
Hope this fixes your issue. If it doesn't please let me know.