Add isWritableFileEntry to the fileSystem API

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

Index: chrome/test/data/extensions/api_test/file_system/is_writable_file_entry/test.js
diff --git a/chrome/test/data/extensions/api_test/file_system/is_writable_file_entry/test.js b/chrome/test/data/extensions/api_test/file_system/is_writable_file_entry/test.js
new file mode 100644
index 0000000000000000000000000000000000000000..89c712217ac55ff6a4c621acc9f5ef446a22cc8c
--- /dev/null
+++ b/chrome/test/data/extensions/api_test/file_system/is_writable_file_entry/test.js
@@ -0,0 +1,27 @@
+// Copyright (c) 2012 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.
+
+chrome.test.runTests([
+  function isWritableEntry() {
+    chrome.fileSystem.chooseFile({type: 'saveFile'},
+        chrome.test.callbackPass(function(entry) {
+      chrome.test.assertEq('writable.txt', entry.name);
+      // Test that the file is writable, as we requested a 'saveFile'.
+      chrome.fileSystem.isWritableFileEntry(entry, chrome.test.callbackPass(
+          function(isWritable) {
+        chrome.test.assertTrue(isWritable);
+      }));
+    }));
+  },
+  function isNotWritableEntry() {
+    chrome.fileSystem.chooseFile(chrome.test.callbackPass(function(entry) {
+      chrome.test.assertEq('writable.txt', entry.name);
+      // The file should not be writable, since the default is 'openFile'.
+      chrome.fileSystem.isWritableFileEntry(entry, chrome.test.callbackPass(
+          function(isWritable) {
+        chrome.test.assertFalse(isWritable);
+      }));
+    }));
+  }
+]);