[VideoSplash] Fix focus issue of VSS and refactors

[VideoSplash] Fix focus issue of VSS and refactors

[PROBLEM] Before the update to VSS's player, the WRT.js could
          call WRT.hideSplashScreen(...), with one window show
          (after 'ready-to-show').

          With VSS player reacting to focus steal, now showing
          the window will result in premature playback stop.

[SOLUTION] With change in WRT interface in libchromium the
           WebApplication can now check, if the reason for
           hiding was valid.

           Side effect is, if the RENDERED was not a valid reason
           to hide a window, the window is not shown at any other
           event. The additional show() is therefore added to
           LOADFINISHED and CUSTOM (VIDEOFINISHED and CUSTOM's
           show() is already in the Chromium patch).

NOTE: part of this change was provided in Chromium project as change
[259340][1]. To have current change compile, you either have to have
chromium RPM with its change, or -- after first unsuccessfull build --
go to your GBS scratch area, into /usr/include/wrt/ and edit the
native_wrtjs.d.ts to have WRT.hideSplashScreen method return `boolean`.

[1]: https://review.tizen.org/gerrit/c/259340

Change-Id: Id63f6b4192cdc9da8da1e4ff0296f11bc15b10b3
Bug-Id: https://cam.sprc.samsung.pl/browse/WPMEDMAIN-2915
Signed-off-by: Marcin Zdun <m.zdun@samsung.com>
Signed-off-by: DongHyun Song <dh81.song@samsung.com>