mediaview: Mount ARC documents provider file system volumes.

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 689e56aa5020e9f6204088ff1f14818d30f1e1e3..6adb969c557e2b359f84603a2dd30d62e979bd85 100644
--- a/chrome/browser/chromeos/arc/arc_service_launcher.cc
+++ b/chrome/browser/chromeos/arc/arc_service_launcher.cc
@@ -98,8 +98,10 @@ void ArcServiceLauncher::Initialize() {
       base::MakeUnique<ArcBootPhaseMonitorBridge>(arc_bridge_service));
   arc_service_manager_->AddService(
       base::MakeUnique<ArcClipboardBridge>(arc_bridge_service));
-  arc_service_manager_->AddService(
-      base::MakeUnique<ArcFileSystemService>(arc_bridge_service));
+  auto file_system_service =
+      base::MakeUnique<ArcFileSystemService>(arc_bridge_service);
+  arc_service_manager_->set_file_system_service(file_system_service.get());
+  arc_service_manager_->AddService(std::move(file_system_service));
   arc_service_manager_->AddService(base::MakeUnique<ArcCrashCollectorBridge>(
       arc_bridge_service, arc_service_manager_->blocking_task_runner()));
   arc_service_manager_->AddService(