[gvfs] google: Add comment for mutex

[Ondrej Holy <oholy src gnome org>]

commit 42909185bd989dcc625b31c146db5948ecb0673a
Author: Ondrej Holy <oholy redhat com>
Date:   Fri Aug 11 13:02:51 2017 +0200

    google: Add comment for mutex
    
    It is not obvious that the mutex guards cache for multi-threaded access.
    Let's add an comment.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=785870

 daemon/gvfsbackendgoogle.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/daemon/gvfsbackendgoogle.c b/daemon/gvfsbackendgoogle.c
index 7bed608..e68c830 100644
--- a/daemon/gvfsbackendgoogle.c
+++ b/daemon/gvfsbackendgoogle.c
@@ -58,7 +58,7 @@ struct _GVfsBackendGoogle
   GHashTable *dir_entries;
   GHashTable *monitors;
   GList *dir_collisions;
-  GRecMutex mutex;
+  GRecMutex mutex; /* guards cache */
   GoaClient *client;
   gboolean entries_stale;
   gchar *account_identity;