Add with_robustness and handle robustness on all implementations

src/api/cocoa/mod.rs

@@ -13,6 +13,7 @@ use GlContext;
 use GlProfile;
 use GlRequest;
 use PixelFormat;
+use Robustness;
 use native_monitor::NativeMonitorId;
 
 use objc::runtime::{Class, Object, Sel, BOOL, YES, NO};
@@ -332,6 +333,13 @@ impl Window {
             unimplemented!()
         }
 
+        match builder.gl_robustness {
+            Robustness::RobustNoResetNotification | Robustness::RobustLoseContextOnReset => {
+                return Err(CreationError::NotSupported);
+            },
+            _ => ()
+        }
+
         let app = match Window::create_app() {
             Some(app) => app,
             None      => { return Err(OsError(format!("Couldn't create NSApplication"))); },