Notify Files App when ARC++ app is installed/removed

components/arc/arc_service_manager.cc

Index: components/arc/arc_service_manager.cc
diff --git a/components/arc/arc_service_manager.cc b/components/arc/arc_service_manager.cc
index d6a68dc335c570ffab4f8f0d34ecc31adb816632..403b5f28f87f83722fdfa67e46bb2810da9c13c8 100644
--- a/components/arc/arc_service_manager.cc
+++ b/components/arc/arc_service_manager.cc
@@ -66,6 +66,19 @@ void ArcServiceManager::AddService(std::unique_ptr<ArcService> service) {
   services_.emplace_back(std::move(service));
 }
 
+void ArcServiceManager::AddObserver(Observer* observer) {
+  observer_list_.AddObserver(observer);
+}
+
+void ArcServiceManager::RemoveObserver(Observer* observer) {
+  observer_list_.RemoveObserver(observer);
+}
+
+void ArcServiceManager::OnAppsUpdated() {
+  for (auto& observer : observer_list_)
+    observer.OnAppsUpdated();
+}
+
 void ArcServiceManager::Shutdown() {
   icon_loader_ = nullptr;
   activity_resolver_ = nullptr;