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

chrome/browser/chromeos/arc/arc_service_launcher.cc

Index: chrome/browser/chromeos/arc/arc_service_launcher.cc
diff --git a/chrome/browser/chromeos/arc/arc_service_launcher.cc b/chrome/browser/chromeos/arc/arc_service_launcher.cc
index 02c4d295b25a89f1eec654f7e0dd81a6821fa0c2..af50b1aefb23c3b74277b7d3b4c1ce583a3f6c7d 100644
--- a/chrome/browser/chromeos/arc/arc_service_launcher.cc
+++ b/chrome/browser/chromeos/arc/arc_service_launcher.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/chromeos/arc/arc_service_launcher.h"
 
+#include <utility>
+
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/chromeos/arc/arc_auth_service.h"
@@ -97,9 +99,13 @@ void ArcServiceLauncher::Initialize() {
       base::MakeUnique<ArcDownloadsWatcherService>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcEnterpriseReportingService>(arc_bridge_service));
-  arc_service_manager_->AddService(base::MakeUnique<ArcIntentHelperBridge>(
+  auto intent_helper = base::MakeUnique<ArcIntentHelperBridge>(
       arc_bridge_service, arc_service_manager_->icon_loader(),
-      arc_service_manager_->activity_resolver()));
+      arc_service_manager_->activity_resolver());
+  // We don't have to remove observer since
+  // ArcServiceManager always outlives ArcIntentHelperBridge.
+  intent_helper->AddObserver(arc_service_manager_.get());
+  arc_service_manager_->AddService(std::move(intent_helper));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcImeService>(arc_bridge_service));
   arc_service_manager_->AddService(