Reject filesystem root entries as args for chrome.fileSystem functions.

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

Index: chrome/browser/extensions/api/file_system/file_system_apitest.cc
diff --git a/chrome/browser/extensions/api/file_system/file_system_apitest.cc b/chrome/browser/extensions/api/file_system/file_system_apitest.cc
index a6b206961261076e51f25a86171c9fa8b197f969..b65a39abb57ed877c31b9889d494ab1c2609230a 100644
--- a/chrome/browser/extensions/api/file_system/file_system_apitest.cc
+++ b/chrome/browser/extensions/api/file_system/file_system_apitest.cc
@@ -553,6 +553,16 @@ IN_PROC_BROWSER_TEST_F(FileSystemApiTest,
       "api_test/file_system/get_writable_file_entry_with_write")) << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(FileSystemApiTest,
+                       FileSystemApiGetWritableRootEntryTest) {
+  base::FilePath test_file = TempFilePath("writable.txt", true);
+  ASSERT_FALSE(test_file.empty());
+  FileSystemChooseEntryFunction::SkipPickerAndAlwaysSelectPathForTest(
+      &test_file);
+  ASSERT_TRUE(RunPlatformAppTest(
+      "api_test/file_system/get_writable_root_entry")) << message_;
+}
+
 IN_PROC_BROWSER_TEST_F(FileSystemApiTest, FileSystemApiIsWritableTest) {
   base::FilePath test_file = TempFilePath("writable.txt", true);
   ASSERT_FALSE(test_file.empty());