monitor-manager: Don't try to match the outputs on hotplug

meta_monitor_config_match_current() only matches the number of outputs
and if the output connector, vendor, product and serial match.

In the X backend, this means that we can't use it to bypass doing any
work because it won't detect cases where we actually want to update
ourselves like e.g. an output being turned off either by us or by
another X client (e.g. xrandr).

In the native backend, unlike the xrandr backend, we only get called
on real hotplug events and thus should always trigger the common
hotplug code to (possibly) apply a new mode so the check is pointless
anyway.

https://bugzilla.gnome.org/show_bug.cgi?id=738630

src/backends/meta-monitor-config.c

@@ -796,27 +796,6 @@ make_config_key (MetaConfiguration *key,
   key->n_outputs = o;
 }
 
-gboolean
-meta_monitor_config_match_current (MetaMonitorConfig  *self,
-                                   MetaMonitorManager *manager)
-{
-  MetaOutput *outputs;
-  unsigned n_outputs;
-  MetaConfiguration key;
-  gboolean ok;
-
-  if (self->current == NULL)
-    return FALSE;
-
-  outputs = meta_monitor_manager_get_outputs (manager, &n_outputs);
-
-  make_config_key (&key, outputs, n_outputs, -1);
-  ok = config_equal (&key, self->current);
-
-  config_clear (&key);
-  return ok;
-}
-
 gboolean
 meta_monitor_manager_has_hotplug_mode_update (MetaMonitorManager *manager)
 {

src/backends/meta-monitor-config.h

@@ -36,9 +36,6 @@ GType meta_monitor_config_get_type (void) G_GNUC_CONST;
 
 MetaMonitorConfig *meta_monitor_config_new (void);
 
-gboolean           meta_monitor_config_match_current (MetaMonitorConfig  *config,
-                                                      MetaMonitorManager *manager);
-
 gboolean           meta_monitor_config_apply_stored (MetaMonitorConfig  *config,
                                                      MetaMonitorManager *manager);
 

src/backends/native/meta-monitor-manager-kms.c

@@ -912,12 +912,6 @@ on_uevent (GUdevClient *client,
 
   meta_monitor_manager_read_current_config (manager);
 
-  /* If this config matches our existing one, don't bother doing anything. */
-  if (meta_monitor_config_match_current (manager->config, manager))
-    return;
-
-  /* This is a hotplug event, so try to make a configuration for our new
-   * set of outputs. */
   meta_monitor_manager_on_hotplug (manager);
 }
 

src/backends/x11/meta-monitor-manager-xrandr.c

@@ -1069,10 +1069,6 @@ meta_monitor_manager_xrandr_handle_xevent (MetaMonitorManagerXrandr *manager_xra
 
   meta_monitor_manager_read_current_config (manager);
 
-  /* If this config matches our existing one, don't bother doing anything. */
-  if (meta_monitor_config_match_current (manager->config, manager))
-    return TRUE;
-
   hotplug = manager_xrandr->resources->timestamp < manager_xrandr->resources->configTimestamp;
   if (hotplug)
     {