Make it to pause/resume loading while multi window is viewing

Make it to pause/resume loading while multi window is viewing

[Title] Make it to pause/resume loading while multi window is viewing
[Issue#] WEB_1455
[Problem] page loading stops when tap on multiple window icon and not load the page properly, page loading should not stop
[Cause] Oriental and intentional implementation
[Solution] Comparing the competitors, make it to pause/resume in about multi window viewing.
[Team] Browser UI
[Developer] Junghwan kang
[Request] N/A

Change-Id: Ifcc8e4e0779dc73ae178363f171de2eceffd560e