Fix empty tab opened for window.open request.

Fix empty tab opened for window.open request.

[ Problem ]  When already MAX (20) tabs are opened and there is a request
             to window.open from current tab, an empty tab is opened.
[ Cause ]    When new,window callback is triggered, we need to create
             ewk_view and pass it to WebEngine through 'out' argument.
             ewk_view has to be created before the function is exited but
             it was created after user responds to max window popup which
             is very late.
[ Solution ] Immediately creat ewk_view and pass to WebEngine, while
             showing the popup. Based on the user decision, i.e, for
             CANCEL : close the loaded tab, and show the recent tab.
             OK : close the oldest tab and retain the loaded tab.

Also, by default the checkbox in max window popup should be set to state
'unchecked'. This is because, if user selects any button hurrily, then
the user won't be able to get the popup again if checked box was default
'checked'.

Change-Id: I394573100ac04017d5f874a3bcdc1ded036ba08b
Signed-off-by: Gajendra N <gajendra.n@samsung.com>