Cool [Q] How to estimate the power supply capability of my Samsung tablet through otg ?

After much hesitation about the choice for which small otg gadget , I choose this one for its slim and simple looking with a suitable price:

http://www.amazon.com/gp/product/B00GLKI0QE

The following idea is how I design the use situation : The otg is connected to my Nexus 7. And I planned to plug the Samsung Tablet to one of the four usb 3.0 port. As this is not a gadget with its own power adapter. I worried about the power supply issue. I wonder which could be the main part to supply part. Let alone to add other devices to all the usb 3.0 ports.

Is my idea a practical one ? Anybody who has a wise solution is warmly welcomed.