[filebrowser] Historgram for the file browser's open time.

chrome/browser/resources/file_manager/js/mock_chrome.js

 // Copyright (c) 2011 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.
 
 /**
  * Mock out the chrome.fileBrowserPrivate API for use in the harness.
  */
 chrome.fileBrowserPrivate = {
 
   /**
@@ skipping 370 matching lines @@
       chrome.fileBrowserHandler.onExecute.listeners_.push(listener);
     }
   }
 };
 
 chrome.tabs = {
   create: function(createOptions) {
     window.open(createOptions.url);
   }
 };
+
+chrome.experimental = {
+  metrics: {
+    recordTime: function() {},
+    recordUserAction: function() {}
+  }
+};