Refactor MountedDiskMonitior and adds its test.

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

Index: chrome/browser/chromeos/extensions/file_manager/event_router.cc
diff --git a/chrome/browser/chromeos/extensions/file_manager/event_router.cc b/chrome/browser/chromeos/extensions/file_manager/event_router.cc
index fda7013cb281c10fadf23d3e970fa7f1e9e69cb5..9b3a458d603ede4c21ba80cc5fa26e643111c138 100644
--- a/chrome/browser/chromeos/extensions/file_manager/event_router.cc
+++ b/chrome/browser/chromeos/extensions/file_manager/event_router.cc
@@ -32,6 +32,7 @@
 #include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/login/login_state.h"
 #include "chromeos/network/network_handler.h"
 #include "chromeos/network/network_state_handler.h"
@@ -320,7 +321,9 @@ void EventRouter::ObserveFileSystemEvents() {
                                                                 FROM_HERE);
   }
 
-  mounted_disk_monitor_.reset(new MountedDiskMonitor());
+  mounted_disk_monitor_.reset(new MountedDiskMonitor(
+      chromeos::DBusThreadManager::Get()->GetPowerManagerClient(),
+      disk_mount_manager));
 
   pref_change_registrar_->Init(profile_->GetPrefs());