Summary: add a sizing check variable for safety of sizing evaluation when the min size of scroller is changed.
Test Plan:
1. run elementary_test
2. search the sample with "popup" keyword
3. click the Efl Ui Popup Alert Scroll sample
Reviewers: Jaehyun_Cho, jpeg, woohyun, thiepha, Blackmole, cedric
Reviewed By: Jaehyun_Cho
Differential Revision: https://phab.enlightenment.org/D5204