Add background-wide file metadata cache.

ui/file_manager/file_manager/background/js/import_history_unittest.html

Index: ui/file_manager/file_manager/background/js/import_history_unittest.html
diff --git a/ui/file_manager/file_manager/background/js/import_history_unittest.html b/ui/file_manager/file_manager/background/js/import_history_unittest.html
index 4926ddfb0ac5ef2f01d63966325905597c31ceff..2e7b6c03577fd102dc124399df9fe8f84d64ebe7 100644
--- a/ui/file_manager/file_manager/background/js/import_history_unittest.html
+++ b/ui/file_manager/file_manager/background/js/import_history_unittest.html
@@ -11,6 +11,7 @@
 
 <script src="../../common/js/volume_manager_common.js"></script>
 <script src="../../common/js/importer_common.js"></script>
+<script src="../../common/js/lru_cache.js"></script>
 <script src="../../common/js/test_importer_common.js"></script>
 <script src="../../common/js/test_tracker.js"></script>
 <script src="../../common/js/metrics_base.js"></script>
@@ -19,6 +20,7 @@
 <script src="../../common/js/unittest_util.js"></script>
 <script src="../../common/js/util.js"></script>
 
+<script src="metadata_proxy.js"></script>
 <script src="import_history.js"></script>
 <script src="import_history_unittest.js"></script>