[mutter] backends: Add comment to translators in "Switch monitor" string

[Carlos Garnacho <carlosg src gnome org>]

commit 0f0b25767d99dc759ae18242d12cec365f869c7b
Author: Carlos Garnacho <carlosg gnome org>
Date:   Mon Sep 12 19:43:47 2016 +0200

    backends: Add comment to translators in "Switch monitor" string
    
    Without context it's not clear to what it actually refers to. Add some
    context.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=770929

 src/backends/meta-input-settings.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/backends/meta-input-settings.c b/src/backends/meta-input-settings.c
index 8e5a31e..4f693c0 100644
--- a/src/backends/meta-input-settings.c
+++ b/src/backends/meta-input-settings.c
@@ -1704,6 +1704,9 @@ meta_input_settings_get_pad_button_action_label (MetaInputSettings  *input_setti
         return accel;
       }
     case G_DESKTOP_PAD_BUTTON_ACTION_SWITCH_MONITOR:
+      /* TRANSLATORS: This string refers to an action, cycles drawing tablets'
+       * mapping through the available outputs.
+       */
       return g_strdup (_("Switch monitor"));
     case G_DESKTOP_PAD_BUTTON_ACTION_HELP:
       return g_strdup (_("Show on-screen help"));