Add a new ozone switch to enable surfaceless output mode.

ui/ozone/public/ozone_switches.cc

Index: ui/ozone/public/ozone_switches.cc
diff --git a/ui/ozone/public/ozone_switches.cc b/ui/ozone/public/ozone_switches.cc
index 0a9b3ab32a04d7988b95182089ca63f3057fcc7a..8df6c9d99bcc4e1028e6b4d78045f05a774ce4ed 100644
--- a/ui/ozone/public/ozone_switches.cc
+++ b/ui/ozone/public/ozone_switches.cc
@@ -12,4 +12,8 @@ const char kOzonePlatform[] = "ozone-platform";
 // Specify location for image dumps.
 const char kOzoneDumpFile[] = "ozone-dump-file";
 
+// Specify if the accelerated path should use surfaceless rendering. In this
+// mode there is no EGL surface.
+const char kOzoneUseSurfaceless[] = "ozone-use-surfaceless";
+
 }  // namespace switches