Restore application on AE_RESUME.

Bug: XWALK-2578

Signed-off-by: Nicolas Guyomard <nicolas.guyomard@open.eurogiciel.org>
Resume is about resuming the javascript engine (see https://github.com/crosswalk-project/crosswalk/commit/94d0859a0920b991d4294e8ab8969e61bc734888).

This patch is about showing an application that has been previously hidden.

In Tizen an application may be hidden/minimized without suspending the JS engine.
See https://docs.google.com/a/open.eurogiciel.org/document/d/10L9aHQHwl5xXNwNAmn3V9T7pkbdd5DqOWDlBwJxvoGA/edit#heading=h.kz53whwjuj98