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 8445448648c59eb6c8a37b19a1f7a7dd9fc6ef6f..8efa8281bf47ff13257d6a6c4ec0ac9eaf9ecb51 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"
@@ -51,10 +53,14 @@ void ArcServiceLauncher::Initialize() {
   arc_service_manager_->AddService(
       base::MakeUnique<ArcEnterpriseReportingService>(
           arc_service_manager_->arc_bridge_service()));
-  arc_service_manager_->AddService(base::MakeUnique<ArcIntentHelperBridge>(
+  auto intent_helper = base::MakeUnique<ArcIntentHelperBridge>(
       arc_service_manager_->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<ArcPolicyBridge>(
       arc_service_manager_->arc_bridge_service()));
   arc_service_manager_->AddService(base::MakeUnique<ArcPrintService>(