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

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service.h>
 
 #include "chrome/browser/chromeos/app_mode/arc/arc_kiosk_app_service_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/app_list/arc/arc_app_utils.h"
@@ skipping 41 matching lines @@
   if (app_info_ && package_name == app_info_->package_name &&
       activity == app_info_->activity) {
     task_id_ = task_id;
   }
 }
 
 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.

   }
 }
 
 ArcKioskAppService::ArcKioskAppService(Profile* profile, ArcAppListPrefs* prefs)
     : profile_(profile), prefs_(prefs) {
   if (prefs_)
     prefs_->AddObserver(this);
   app_manager_ = ArcKioskAppManager::Get();
   if (app_manager_) {
     app_manager_->AddObserver(this);
@@ skipping 38 matching lines @@
   std::unordered_set<std::string> app_ids =
       prefs_->GetAppsForPackage(app->app_info().package_name());
   if (app_ids.empty())
     return std::string();
   // TODO(poromov@): Choose appropriate app id to launch. See
   // http://crbug.com/665904
   return std::string(*app_ids.begin());
 }
 
 }  // namespace chromeos