Add custom interstitial for captive portals.

chrome/browser/resources/ssl/captive_portal.js

+// Copyright 2014 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.
+
+var expandedDetails = false;
+var CMD_OPEN_LOGIN_PAGE = 1;
+var CMD_MORE = 2;
+
+function sendCommand(cmd) {
+  window.domAutomationController.setAutomationId(1);
+  window.domAutomationController.send(cmd);
+}
+
+function setupEvents() {
+  $('primary-button').addEventListener('click', function() {
+      sendCommand(CMD_OPEN_LOGIN_PAGE);
+  });
+
+  $('details-button').addEventListener('click', function(event) {
+    var hiddenDetails = $('details').classList.toggle('hidden');
+    $('details-button').innerText = hiddenDetails ?
+        loadTimeData.getString('openDetails') :
+        loadTimeData.getString('closeDetails');
+    if (!expandedDetails) {
+      // Record a histogram entry only the first time that details is opened.
+      sendCommand(CMD_MORE);
+      expandedDetails = true;
+    }
+    event.preventDefault();
+  });
+}
+
+document.addEventListener('DOMContentLoaded', setupEvents);