sharing: Remember the password on remote desktop sharing

If we are going through mutter's RemoteDesktop interface, we don't
seemingly remember the password set. Add support for reading it
from secrets and change the entry password on dialog construction,
to bring it on par with our vino handling.

panels/sharing/cc-gnome-remote-desktop.c

@@ -169,3 +169,19 @@ cc_grd_on_vnc_password_entry_notify_text (GtkEntry   *entry,
                          cancellable, on_password_stored, entry,
                          NULL);
 }
+
+void
+cc_grd_update_password_entry (GtkEntry *entry)
+{
+  g_autoptr(GError) error = NULL;
+  g_autofree gchar *password = NULL;
+
+  password = secret_password_lookup_sync (CC_GRD_VNC_PASSWORD_SCHEMA,
+                                          NULL, &error,
+                                          NULL);
+  if (error)
+    g_warning ("Failed to get password: %s", error->message);
+
+  if (password)
+    gtk_entry_set_text (entry, password);
+}

panels/sharing/cc-gnome-remote-desktop.h

@@ -47,4 +47,6 @@ void cc_grd_on_vnc_password_entry_notify_text (GtkEntry   *entry,
                                                GParamSpec *pspec,
                                                gpointer    user_data);
 
+void cc_grd_update_password_entry (GtkEntry *entry);
+
 G_END_DECLS

panels/sharing/cc-sharing-panel.c

@@ -1110,6 +1110,8 @@ cc_sharing_panel_setup_screen_sharing_dialog_gnome_remote_desktop (CcSharingPane
                     G_CALLBACK (screen_sharing_hide_cb),
                     self);
 
+  cc_grd_update_password_entry (self->remote_control_password_entry);
+
   /* accept at most 8 bytes in password entry */
   g_signal_connect (self->remote_control_password_entry,
                     "insert-text",