Add isWritableFileEntry to the fileSystem API

chrome/browser/extensions/api/file_system/file_system_apitest.cc

 // 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.
 
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "chrome/browser/extensions/api/file_system/file_system_api.h"
 #include "chrome/browser/extensions/platform_app_browsertest_util.h"
 
 using extensions::FileSystemChooseFileFunction;
@@ skipping 170 matching lines @@
 
 IN_PROC_BROWSER_TEST_F(FileSystemApiTest,
     FileSystemApiGetWritableWithWriteTest) {
   FilePath test_file = TempFilePath("writable.txt", true);
   ASSERT_FALSE(test_file.empty());
   FileSystemChooseFileFunction::SkipPickerAndAlwaysSelectPathForTest(
       &test_file);
   ASSERT_TRUE(RunPlatformAppTest(
       "api_test/file_system/get_writable_file_entry_with_write")) << message_;
 }
+
+IN_PROC_BROWSER_TEST_F(FileSystemApiTest, FileSystemApiIsWritableTest) {
+  FilePath test_file = TempFilePath("writable.txt", true);
+  ASSERT_FALSE(test_file.empty());
+  FileSystemChooseFileFunction::SkipPickerAndAlwaysSelectPathForTest(
+      &test_file);
+  ASSERT_TRUE(RunPlatformAppTest(
+      "api_test/file_system/is_writable_file_entry")) << message_;
+}