Release resources regarding buffer explicitly on resizing Box if needed

Release resources regarding buffer explicitly on resizing Box if needed

[Issue#] N/A
[Problem] Sometimes existing resources regarding buffer is not released on resizing Box
[Cause] when ecore_evas_resize function is called,
        sometimes the function doesn't call specific callback regarding freeing resources that is registed by web-provider
[Solution] Beforing allocating new buffer on resizing Box,
           web-provider lets existing buffer be released explicitly if it has been not released yet.

Change-Id: I9efbceba92ffdf236a6cf018da608fb06265b777