Allow to pass remount option to Mount method of cros_disks_client.

chromeos/dbus/cros_disks_client.h

Index: chromeos/dbus/cros_disks_client.h
diff --git a/chromeos/dbus/cros_disks_client.h b/chromeos/dbus/cros_disks_client.h
index c6e2f971bcb9273f8b49de993fe186c83f12238a..ec951e4ca218843ecca39e33567babb99e925926 100644
--- a/chromeos/dbus/cros_disks_client.h
+++ b/chromeos/dbus/cros_disks_client.h
@@ -108,6 +108,12 @@ enum MountAccessMode {
   MOUNT_ACCESS_MODE_READ_ONLY,
 };
 
+// Whether to mount to a new path or remount an existing one.

[hashimoto, 2016/10/19 08:46:23]

What does "remount an existing one" mean?
Please clarify what happens with each option.

IIUC when an already mounted disk is mounted again, mount fails with
REMOUNT_OPTION_DISABLED unless unmount is done before, while it succeeds with
REMOUNT_OPTION_ENABLED.
Am I understanding it right?
Also, what happens if REMOUNT_OPTION_ENABLED is used against a disk which hasn't
mounted yet?

BTW, why doesn't CrosDisks automatically adds "remount" to the options when
mounting an already mounted disk?

[yamaguchi1, 2016/10/19 10:34:10]

Revised the comments.
I made it this way to minimize the change preserving existing behavior which
have been returning errors for duplicated mount attempts.
Now I think we may change it (by another patch), if there is no special need to
fail mounting same device twice from Chrome.

+enum RemountOption {
+  REMOUNT_OPTION_DISABLED,
+  REMOUNT_OPTION_ENABLED,
+};
+
 // A class to represent information about a disk sent from cros-disks.
 class CHROMEOS_EXPORT DiskInfo {
  public:
@@ -278,6 +284,7 @@ class CHROMEOS_EXPORT CrosDisksClient : public DBusClient {
                      const std::string& source_format,
                      const std::string& mount_label,
                      MountAccessMode access_mode,
+                     RemountOption remount,
                      const base::Closure& callback,
                      const base::Closure& error_callback) = 0;
 
@@ -341,7 +348,8 @@ class CHROMEOS_EXPORT CrosDisksClient : public DBusClient {
   // Composes a list of mount options.
   static std::vector<std::string> ComposeMountOptions(
       const std::string& mount_label,
-      MountAccessMode access_mode);
+      MountAccessMode access_mode,
+      RemountOption remount);
 
  protected:
   // Create() should be used instead.