Introduce ArcServiceManager::OnShutdown().

For graceful shutdown, this CL introduces OnShutdown
observer callback.
Along with the change, EventRouter now properly calls RemoveObserver
in the callback.
ArcServiceManager::IsInitialized() is now no longer needed. Remove it.

BUG=672829
TEST=Ran bots.

Review-Url: https://codereview.chromium.org/2581953002
Cr-Commit-Position: refs/heads/master@{#439144}

chrome/browser/chromeos/extensions/file_manager/event_router.cc

@@ -401,8 +401,13 @@ EventRouter::EventRouter(Profile* profile)
 
 EventRouter::~EventRouter() = default;
 
+void EventRouter::OnArcShutdown() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  arc::ArcServiceManager::Get()->RemoveObserver(this);
+}
+
 void EventRouter::OnIntentFiltersUpdated() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   BroadcastEvent(profile_,
                  extensions::events::FILE_MANAGER_PRIVATE_ON_APPS_UPDATED,
                  file_manager_private::OnAppsUpdated::kEventName,
@@ -412,9 +417,6 @@ void EventRouter::OnIntentFiltersUpdated() {
 void EventRouter::Shutdown() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
-  if (arc::ArcServiceManager::IsInitialized())
-    arc::ArcServiceManager::Get()->RemoveObserver(this);
-
   chromeos::system::TimezoneSettings::GetInstance()->RemoveObserver(this);
 
   DLOG_IF(WARNING, !file_watchers_.empty())

chrome/browser/chromeos/extensions/file_manager/event_router.h

@@ -68,6 +68,7 @@ class EventRouter : public KeyedService,
   ~EventRouter() override;
 
   // arc::ArcServiceManager::Observer overrides.
+  void OnArcShutdown() override;
   void OnIntentFiltersUpdated() override;
 
   // KeyedService overrides.

components/arc/arc_service_manager.cc

@@ -83,14 +83,6 @@ ArcServiceManager* ArcServiceManager::Get() {
   return g_arc_service_manager;
 }
 
-// static
-bool ArcServiceManager::IsInitialized() {
-  if (!g_arc_service_manager)
-    return false;
-  DCHECK(g_arc_service_manager->thread_checker_.CalledOnValidThread());
-  return true;
-}
-
 ArcBridgeService* ArcServiceManager::arc_bridge_service() {
   DCHECK(thread_checker_.CalledOnValidThread());
   return arc_bridge_service_.get();
@@ -113,6 +105,11 @@ void ArcServiceManager::RemoveObserver(Observer* observer) {
 
 void ArcServiceManager::Shutdown() {
   DCHECK(thread_checker_.CalledOnValidThread());
+
+  // Before actual shutdown, notify observers for clean up.
+  for (auto& observer : observer_list_)
+    observer.OnArcShutdown();
+
   icon_loader_ = nullptr;
   activity_resolver_ = nullptr;
   services_.clear();

components/arc/arc_service_manager.h

@@ -28,6 +28,11 @@ class ArcServiceManager {
  public:
   class Observer {
    public:
+    // Called when ArcServiceManager is being shut down. Observer
+    // implementation should clean up ARC related stuff here. One of the
+    // typical use cases is calling ArcServiceManager::RemoveObserver().
+    virtual void OnArcShutdown() = 0;
+
     // Called when intent filters are added or removed.
     virtual void OnIntentFiltersUpdated() = 0;
 
@@ -50,12 +55,6 @@ class ArcServiceManager {
   // called on the thread that this class was created on.
   static ArcServiceManager* Get();
 
-  // Returns if the ARC Service Manager instance exists.
-  // DO NOT CALL THIS. This function is a dirty workaround for properly shutting
-  // down chrome/browser/chromeos/extensions/file_manager/event_router.cc, and
-  // will likely be removed in the future.
-  static bool IsInitialized();
-
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);