Fix filesystem API file_handlers to work for drive on ChromeOS.

chrome/browser/chromeos/extensions/external_filesystem_apitest.cc

Index: chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
diff --git a/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc b/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
index df0166ffd4dc64168194486373a4cc39fce6d670..2e427140add933ee897d7c2bfc79dd152ed23d39 100644
--- a/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
+++ b/chrome/browser/chromeos/extensions/external_filesystem_apitest.cc
@@ -511,4 +511,12 @@ IN_PROC_BROWSER_TEST_F(DriveFileSystemExtensionApiTest, Search) {
       FLAGS_NONE)) << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(DriveFileSystemExtensionApiTest, AppFileHanlder) {
+  EXPECT_TRUE(RunFileSystemExtensionApiTest(
+      "file_browser/handler_test_runner",
+      FILE_PATH_LITERAL("manifest_v2.json"),
+      "file_browser/app_file_handler",
+      FLAGS_USE_FILE_HANDLER)) << message_;
+}
+
 }  // namespace