Add support for directory access to the file system API.

chrome/test/data/extensions/api_test/file_system/restore_directory/test.js

Index: chrome/test/data/extensions/api_test/file_system/restore_directory/test.js
diff --git a/chrome/test/data/extensions/api_test/file_system/restore_entry/test.js b/chrome/test/data/extensions/api_test/file_system/restore_directory/test.js
similarity index 64%
copy from chrome/test/data/extensions/api_test/file_system/restore_entry/test.js
copy to chrome/test/data/extensions/api_test/file_system/restore_directory/test.js
index ff1e66f35df45a7179c826dfed1d06b80997c104..40843328dacc8455d7baef1c302233f6d7c566e9 100644
--- a/chrome/test/data/extensions/api_test/file_system/restore_entry/test.js
+++ b/chrome/test/data/extensions/api_test/file_system/restore_directory/test.js
@@ -12,16 +12,14 @@ chrome.test.runTests([
     chrome.fileSystem.restoreEntry(id, chrome.test.callbackPass(
         function(restoredEntry) {
       chrome.test.assertTrue(restoredEntry != null);
+      chrome.test.assertTrue(restoredEntry.isDirectory);
       chrome.test.assertEq(
           chrome.fileSystem.retainEntry(restoredEntry), id);
-      checkEntry(restoredEntry, 'writable.txt', false /* isNew */,
-                 true /*shouldBeWritable */);
+      restoredEntry.getFile(
+          'writable.txt', {}, chrome.test.callback(function(entry) {
+        checkEntry(entry, 'writable.txt', false /* isNew */,
+                   true /*shouldBeWritable */);
       }));
-    chrome.fileSystem.isRestorable('wrong id', chrome.test.callbackPass(
-        function(isRestorable) {
-      chrome.test.assertFalse(isRestorable);
     }));
-    chrome.fileSystem.restoreEntry('wrong id', chrome.test.callbackFail(
-        'Unknown id'));
   }
 ]);