Add a mechanism to ignore certain elements for accessibility audit on a per-test basis.

chrome/test/data/webui/test_api.js

Index: chrome/test/data/webui/test_api.js
diff --git a/chrome/test/data/webui/test_api.js b/chrome/test/data/webui/test_api.js
index 04e7d4df84511d6a30979238387e7b35bd9baa5b..c403588dedb8cdf48b7d0c4f1a09177d2010aeb2 100644
--- a/chrome/test/data/webui/test_api.js
+++ b/chrome/test/data/webui/test_api.js
@@ -888,7 +888,7 @@ var testing = {};
    * @private
    */
   function runAccessibilityAudit(a11yErrors, a11yWarnings) {
-    var auditResults = axs.Audit.run();
+    var auditResults = axs.Audit.run(this.auditConfig);
     for (var i = 0; i < auditResults.length; i++) {
       var auditResult = auditResults[i];
       if (auditResult.result == axs.constants.AuditResult.FAIL) {