Revert of Move file_handlers API from //chrome to //extensions

extensions/browser/api/file_handlers/BUILD.gn

Index: extensions/browser/api/file_handlers/BUILD.gn
diff --git a/extensions/browser/api/file_handlers/BUILD.gn b/extensions/browser/api/file_handlers/BUILD.gn
deleted file mode 100644
index 03b261ad532352f7848233e2581f744f993f963f..0000000000000000000000000000000000000000
--- a/extensions/browser/api/file_handlers/BUILD.gn
+++ /dev/null
@@ -1,14 +0,0 @@
-# Copyright 2017 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.
-
-source_set("file_handlers") {
-  sources = [
-    "app_file_handler_util.cc",
-    "app_file_handler_util.h",
-    "directory_util.cc",
-    "directory_util.h",
-    "mime_util.cc",
-    "mime_util.h",
-  ]
-}