LibGfx: Enumerate metric theme roles

This change does practically nothing except that you no longer have to
put new roles there, as they are now automatically read from the enum
list.

Userland/Libraries/LibGfx/SystemTheme.cpp

@@ -77,12 +77,11 @@ Core::AnonymousBuffer load_system_theme(Core::ConfigFile const& file)
     ENUMERATE_COLOR_ROLES(__ENUMERATE_COLOR_ROLE)
 #undef __ENUMERATE_COLOR_ROLE
 
-#define DO_METRIC(x) \
-    data->metric[(int)MetricRole::x] = get_metric(#x, (int)MetricRole::x)
-
-    DO_METRIC(TitleHeight);
-    DO_METRIC(TitleButtonWidth);
-    DO_METRIC(TitleButtonHeight);
+#undef __ENUMERATE_METRIC_ROLE
+#define __ENUMERATE_METRIC_ROLE(role) \
+    data->metric[(int)MetricRole::role] = get_metric(#role, (int)MetricRole::role);
+    ENUMERATE_METRIC_ROLES(__ENUMERATE_METRIC_ROLE)
+#undef __ENUMERATE_METRIC_ROLE
 
 #define DO_PATH(x, allow_empty)                                                                                  \
     do {                                                                                                         \