Add the browser test for the new gallery.

chrome/test/data/extensions/api_test/file_manager_browsertest/gallery/test_loader.js

Index: chrome/test/data/extensions/api_test/file_manager_browsertest/gallery/test_loader.js
diff --git a/chrome/test/data/extensions/api_test/file_manager_browsertest/gallery/test_loader.js b/chrome/test/data/extensions/api_test/file_manager_browsertest/gallery/test_loader.js
new file mode 100644
index 0000000000000000000000000000000000000000..b4216be8d6f8236ca9f3ef95c75d4e9272a9359a
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/file_manager_browsertest/gallery/test_loader.js
@@ -0,0 +1,55 @@
+// Copyright (c) 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.
+
+'use strict';
+
+/**
+ * Loads a test script from URL.
+ * @param {string} url URL of a script file.
+ * @return {Promise} Promise to be fulfilled when completing to load.
+ */
+function loadScript(url) {
+  return new Promise(function(fulfill, reject) {
+    var script = document.createElement('script');
+    script.src = url;
+    // Ensure the scripts are loaded in the order of calling loadScript.
+    script.async = false;
+    script.onload = fulfill;
+    script.onerror = reject.bind(null, 'Faile to load ' + url);
+    document.documentElement.appendChild(script);
+  });
+}
+
+var testUtilPromise = loadScript(
+    'chrome-extension:///ejhcmmdhhpdhhgmifplfmjobgegbibkn/test_util.js');
+
+testUtilPromise.then(function() {
+  var inGuestModePromise = sendTestMessage({name: 'isInGuestMode'});
+  var testNamePromise = sendTestMessage({name: 'getTestName'});
+  var scriptsPromise = sendTestMessage({name: 'getScripts'});
+  Promise.all([inGuestModePromise, testNamePromise, scriptsPromise]).then(
+      function(args) {
+        // Do nothing if the guest mode is different.
+        if (JSON.parse(args[0]) !== chrome.extension.inIncognitoContext)
+          return;
+        var scripts = JSON.parse(args[2]);
+        return Promise.all(scripts.map(loadScript)).then(function() {
+          var testName = args[1];
+          var testCase = function() {
+            var success = chrome.test.callbackPass();
+            Promise.resolve().then(function() {
+              return window[testName]();
+            }).then(function() {
+              success();
+            }, function(error) {
+              chrome.test.fail(error.stack || error);
+            });
+          };
+          testCase.generatedName = testName;
+          chrome.test.runTests([testCase]);
+        });
+      });
+}).catch(function(error) {
+  chrome.test.fail(error.stack || error);
+});