Move free disk space check to session_manager.

chromeos/dbus/session_manager_client.h

Index: chromeos/dbus/session_manager_client.h
diff --git a/chromeos/dbus/session_manager_client.h b/chromeos/dbus/session_manager_client.h
index ee142aad64cd384fafa03c44ef9c46683b5c2d7c..f2c89cc01b08402b4c3df623ceb7fae2e8ff9d25 100644
--- a/chromeos/dbus/session_manager_client.h
+++ b/chromeos/dbus/session_manager_client.h
@@ -231,12 +231,20 @@ class CHROMEOS_EXPORT SessionManagerClient : public DBusClient {
   // Asynchronously starts the ARC instance for the user whose cryptohome is
   // located by |cryptohome_id|.  Flag |disable_boot_completed_broadcast|
   // blocks Android ACTION_BOOT_COMPLETED broadcast for 3rd party applications.
-  // Upon completion, invokes |callback| with the result; true on success, false
-  // on failure (either session manager failed to start an instance or session
-  // manager can not be reached).
+  // Upon completion, invokes |callback| with the result.
+  // Running ARC requires some amount of disk space. LOW_FREE_DISK_SPACE will
+  // be returned when there is not enough free disk space for ARC.
+  // UNKNOWN_ERROR is returned for any other errors.
+  // TODO(hidehiko): Replace "typedef" by "using".
+  enum class StartArcInstanceResult {
+    SUCCESS,
+    UNKNOWN_ERROR,
+    LOW_FREE_DISK_SPACE,
+  };
+  typedef base::Callback<void(StartArcInstanceResult)> StartArcInstanceCallback;
   virtual void StartArcInstance(const cryptohome::Identification& cryptohome_id,
                                 bool disable_boot_completed_broadcast,
-                                const ArcCallback& callback) = 0;
+                                const StartArcInstanceCallback& callback) = 0;
 
   // Asynchronously stops the ARC instance.  Upon completion, invokes
   // |callback| with the result; true on success, false on failure (either