[mutter] monitor-manager-xrandr: don't set underscan property when not supported

[Jasper St. Pierre <jstpierre src gnome org>]

commit 659b8ed471b49b583e8bc30d99bbdb6bb8d44c3e
Author: Cosimo Cecchi <cosimoc gnome org>
Date:   Wed Jul 1 17:59:36 2015 -0700

    monitor-manager-xrandr: don't set underscan property when not supported
    
    We should not be setting random output properties like this.
    Use the function we just introduced to only set the underscan flag when
    it's actually supported.

 src/backends/x11/meta-monitor-manager-xrandr.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/backends/x11/meta-monitor-manager-xrandr.c b/src/backends/x11/meta-monitor-manager-xrandr.c
index 86d24b5..dd10c38 100644
--- a/src/backends/x11/meta-monitor-manager-xrandr.c
+++ b/src/backends/x11/meta-monitor-manager-xrandr.c
@@ -1209,9 +1209,10 @@ meta_monitor_manager_xrandr_apply_configuration (MetaMonitorManager *manager,
                                       output_info->output,
                                       output_info->is_presentation);
 
-      output_set_underscanning_xrandr (manager_xrandr,
-                                       output_info->output,
-                                       output_info->is_underscanning);
+      if (output_get_supports_underscanning_xrandr (manager_xrandr, output_info->output))
+        output_set_underscanning_xrandr (manager_xrandr,
+                                         output_info->output,
+                                         output_info->is_underscanning);
 
       output->is_primary = output_info->is_primary;
       output->is_presentation = output_info->is_presentation;