[File Manager] Properly enable/disable Copy and Open for GData files in the offline mode.

chrome/browser/resources/file_manager/js/util.js

Index: chrome/browser/resources/file_manager/js/util.js
diff --git a/chrome/browser/resources/file_manager/js/util.js b/chrome/browser/resources/file_manager/js/util.js
index d51879bf2f901657f613b50a91a61687a30bf223..eb39b1b8a08c5554754f476fb303f15d3efca309 100644
--- a/chrome/browser/resources/file_manager/js/util.js
+++ b/chrome/browser/resources/file_manager/js/util.js
@@ -491,5 +491,13 @@ var util = {
            (event.altKey ? 'Alt-' : '') +
            (event.shiftKey ? 'Shift-' : '') +
            (event.metaKey ? 'Meta-' : '');
+  },
+
+  /**
+   * A wrapper for navigator.onLine that allows for easy debug override.
+   * @return {boolean} True if offline.
+   */
+  isOffline: function() {
+    return !navigator.onLine;
   }
 };