Allow to pass remount option to Mount method of cros_disks.
The remount option will be handled by cros_disks after this change:
https://chromium-review.googlesource.com/#/c/390410/

BUG=642247

Review-Url: https://chromiumcodereview.appspot.com/2392503002
Cr-Commit-Position: refs/heads/master@{#426792}
diff --git a/chromeos/disks/disk_mount_manager.cc b/chromeos/disks/disk_mount_manager.cc
index c5d3737..493596af 100644
--- a/chromeos/disks/disk_mount_manager.cc
+++ b/chromeos/disks/disk_mount_manager.cc
@@ -80,6 +80,7 @@
     }
     cros_disks_client_->Mount(
         source_path, source_format, mount_label, access_mode,
+        REMOUNT_OPTION_MOUNT_NEW_DEVICE,
         // When succeeds, OnMountCompleted will be called by
         // "MountCompleted" signal instead.
         base::Bind(&base::DoNothing),