Remount all removable storage devices upon policy update

chrome/browser/chromeos/file_manager/volume_manager.h

Index: chrome/browser/chromeos/file_manager/volume_manager.h
diff --git a/chrome/browser/chromeos/file_manager/volume_manager.h b/chrome/browser/chromeos/file_manager/volume_manager.h
index 41c13747403f46d26ab954d4fd8d4dd439c0a673..80a1ca853247617cef876efdf15b6b12c59562bc 100644
--- a/chrome/browser/chromeos/file_manager/volume_manager.h
+++ b/chrome/browser/chromeos/file_manager/volume_manager.h
@@ -301,6 +301,9 @@ class VolumeManager : public KeyedService,
   // Called on change to kExternalStorageDisabled pref.
   void OnExternalStorageDisabledChanged();
 
+  // Called on change to kExternalStorageReadOnly pref.
+  void OnExternalStorageReadOnlyChanged();
+
   // RemovableStorageObserver overrides.
   void OnRemovableStorageAttached(
       const storage_monitor::StorageInfo& info) override;