[Files.app] Use dictionary-way to access Entry.cachedUrl

ui/file_manager/file_manager/foreground/js/directory_contents.js

Index: ui/file_manager/file_manager/foreground/js/directory_contents.js
diff --git a/ui/file_manager/file_manager/foreground/js/directory_contents.js b/ui/file_manager/file_manager/foreground/js/directory_contents.js
index f3b8ba3d979d50d78c7f71b62b29e64f42455de9..95266c38cc09e1265621f7094603612b01f31d90 100644
--- a/ui/file_manager/file_manager/foreground/js/directory_contents.js
+++ b/ui/file_manager/file_manager/foreground/js/directory_contents.js
@@ -912,7 +912,9 @@ DirectoryContents.prototype.onNewEntries_ = function(refresh, entries) {
   // Caching URL to reduce a number of calls of toURL in sort.
   // This is a temporary solution. We need to fix a root cause of slow toURL.
   // See crbug.com/370908 for detail.
-  entriesFiltered.forEach(function(entry) { entry.cachedUrl = entry.toURL(); });
+  entriesFiltered.forEach(function(entry) {
+    entry['cachedUrl'] = entry.toURL();
+  });
 
   if (entriesFiltered.length === 0)
     return;