MD Settings: Adding some unit tests for <settings-main>.

chrome/test/data/webui/settings/cr_settings_browsertest.js

Index: chrome/test/data/webui/settings/cr_settings_browsertest.js
diff --git a/chrome/test/data/webui/settings/cr_settings_browsertest.js b/chrome/test/data/webui/settings/cr_settings_browsertest.js
index c205465b39ff0a2b6ddad58f15faa1b5a4cfd860..8378efe5fc02a1680ff5b4834f7bc69621b92882 100644
--- a/chrome/test/data/webui/settings/cr_settings_browsertest.js
+++ b/chrome/test/data/webui/settings/cr_settings_browsertest.js
@@ -682,3 +682,27 @@ TEST_F('CrSettingsNonExistentRouteTest', 'All', function() {
   });
   mocha.run();
 });
+
+/**
+ * Test fixture for chrome/browser/resources/settings/settings_main/.
+ * @constructor
+ * @extends {CrSettingsBrowserTest}
+*/
+function CrSettingsMainPageTest() {}
+
+CrSettingsMainPageTest.prototype = {
+  __proto__: CrSettingsBrowserTest.prototype,
+
+  /** @override */
+  browsePreload: 'chrome://md-settings/settings_main/settings_main.html',
+
+  /** @override */
+  extraLibraries: CrSettingsBrowserTest.prototype.extraLibraries.concat([
+    'settings_main_test.js',
+  ]),
+};
+
+TEST_F('CrSettingsMainPageTest', 'All', function() {
+  settings_main_page.registerTests();
+  mocha.run();
+});