arc: Try to restart ARC++ kiosk app if the task was closed.

chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc

Index: chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc
diff --git a/chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc b/chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc
index 3e54f436ce08f75489b8ed750b4eb85ced66871b..333a95570e0aa75a12c208033da6991c20693a6c 100644
--- a/chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc
+++ b/chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.cc
@@ -59,6 +59,9 @@ void ArcKioskAppService::OnTaskDestroyed(int32_t task_id) {
   if (task_id == task_id_) {
     app_launcher_.reset();
     task_id_ = -1;
+    // Trying to restart app if it was somehow closed or crashed
+    // as kiosk app should always be running during the session.
+    PreconditionsChanged();

[khmel, 2016/12/26 20:29:38]

I found 2 handlers:

ArcKioskAppLauncher::OnTaskCreated
ArcKioskAppService::OnTaskCreated
And it seems that both do the same thing, checking target app 
if (!app || app->package_name != package_name || app->activity != activity)
and setting task_id_.
If so, would it be possible to get rid of duplicate logic?
However this looks outside of scope of this CL so I would be ok in this case to
do it in separate CL, todo b/ is preferred.

nit: please also add TEST= section in desc.

lgtm as task described.

   }
 }