Cancel client auth requests when not promptable.

chrome/test/data/extensions/api_test/xhr/background.js

Index: chrome/test/data/extensions/api_test/xhr/background.js
diff --git a/chrome/test/data/extensions/api_test/xhr/background.js b/chrome/test/data/extensions/api_test/xhr/background.js
new file mode 100644
index 0000000000000000000000000000000000000000..029a20b492c79c1c917f0e58e6fbcfdc3843f84b
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/xhr/background.js
@@ -0,0 +1,13 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+chrome.test.getConfig(function(config) {
+  var xhr = new XMLHttpRequest();
+  xhr.open("GET", config.customArg);
+  xhr.onloadend = function(ev) {
+    // Whether or not the test passed, complete the test.
+    chrome.test.notifyPass();
+  };
+  xhr.send();
+});