Open links in WebView with user's default browser on clicking them

Set policyDelegate of a WebView to some class and implement the delegate method below in the class.

- (void)webView:(WebView *)webView decidePolicyForNavigationAction:(NSDictionary *)actionInformation request:(NSURLRequest *)request frame:(WebFrame *)frame decisionListener:(id < WebPolicyDecisionListener >)listener {
  if ([[actionInformation valueForKey:WebActionNavigationTypeKey] intValue] == WebNavigationTypeLinkClicked) {
    [[NSWorkspace sharedWorkspace] openURL:request.URL];
    [listener ignore];
  } else {
    [listener use];
  }
}

MacAppならありがちな挙動なのに意外とドキュメントに書いてない&探しても見付からなくて時間かかった．ので英語で書いておく．