Use the experimental.webInspector.audits module to add new audit categories and rules to WebInspector's Audit panel.

See WebInspector API summary for general introduction to using WebInspector API.

Notes

Each audit category is represented by a line on Select audits to run screen in the Audits panel. The following example adds a category named Readability:

var category = webInspector.audits.addCategory("Readability", 2);
Extension audit category on the launch screen of Audits panel

If the category's checkbox is checked, the onAuditStarted event of that category will be fired when user clicks the Run button.

The event handler in your extension receives AuditResults as an argument and should add one or more results using addResult() method. This may be done asynchronously, i.e. after the handler returns. The run of the category is considered to be complete once the extension adds the number of results declared when adding the category with experimental.webInspector.audits.addCategory() or calls AuditResult's done() method.

The results may include additional details visualized as an expandable tree by the Audits panel. You may build the details tree using createResult() and addChild() methods. The child node may include specially formatted fragments created by auditResults.snippet() or auditResults.url().

The following example adds a handler for onAuditStarted event that creates two audit results and populates one of them with the additional details: 
category.onAuditStarted.addListener(function(results) {
  var details = results.createResult("Details...");
  var styles = details.addChild("2 styles with small font");
  var elements = details.addChild("3 elements with small font");

  results.addResult("Font Size (5)",
      "5 elements use font size below 10pt",
      results.Severity.Severe,
      details);
  results.addResult("Contrast",
                    "Text should stand out from background",
                    results.Severity.Info);
});

The audit result tree produced by the snippet above will look like this:

Audit results example