Files.app: Reland r261616: Add a test to rename a file.

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

Index: chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
diff --git a/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js b/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
index fb327118243878dfa4ddf28dcd5c883d4182f210..e6f7ee13aed57147db542a4f691b976c3ef62f10 100644
--- a/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
+++ b/chrome/test/data/extensions/api_test/file_manager_browsertest/background.js
@@ -340,6 +340,29 @@ function waitUntilTaskExecutes(windowId, taskId) {
 }
 
 /**
+ * Sends a fake key down event.
+ * @param {string} windowId Window ID.
+ * @param {string} query Query for the target element.
+ * @param {string} keyIdentifer Key identifier.
+ * @param {boolean} ctrlKey Control key flag.
+ * @return {Promise} Promise to be fulfilled or rejected depending on the
+ *     result.
+ */
+function fakeKeyDown(windowId, query, keyIdentifer, ctrlKey) {
+  return new Promise(function(fulfill, reject) {
+    callRemoteTestUtil('fakeKeyDown',
+                       windowId,
+                       [query, keyIdentifer, ctrlKey],
+                       function(result) {
+                         if (result)
+                           fulfill();
+                         else
+                           reject(new Error('Fail to fake key down.'));
+                       });
+  });
+}
+
+/**
  * Executes a sequence of test steps.
  * @constructor
  */
@@ -721,7 +744,7 @@ function setupAndWaitUntilReady(appState, initialRoot, callback) {
  */
 function checkIfNoErrorsOccured(callback) {
   callRemoteTestUtil('getErrorCount', null, [], function(count) {
-    chrome.test.assertEq(0, count);
+    chrome.test.assertEq(0, count, 'The error count is not 0.');
     callback();
   });
 }