MD Settings/Options: add equivalent logs for "time until interactive"

chrome/browser/resources/settings/settings_ui/settings_ui.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'settings-ui' implements the UI for the Settings page.
  *
  * Example:
  *
@@ skipping 140 matching lines @@
 // </if>
       };
     }
 
     this.showAndroidApps_ = loadTimeData.valueExists('androidAppsAllowed') &&
         loadTimeData.getBoolean('androidAppsAllowed');
   },
 
   /** @override */
   attached: function() {
+    setTimeout(function() {
+      chrome.send(
+          'metricsHandler:recordTime',
+          ['Settings.TimeUntilInteractive', window.performance.now()]);

[dpapad, 2017/02/25 01:04:08]

How do we differentiate between old VS new timings? Do we care about the case
where
 1) a user with enabled MD Settings goes to chrome://settings-frame?
 2) a user with disabled MD Settings goes to chrome://md-settings?

Would those mess up the metrics by recording both metrics in the same bucket?

[Dan Beam, 2017/03/04 02:36:05]

i really don't care, to be honest.

in the case of ChromeOS, we really should be comparing against settings-frame. 
that's how users get to settings.

on the case of desktop, we could filter only those on 'chrome://settings', but
like barely anybody does anything other than the typical flow.

i really don't think we need to care about differentiating md-settings nor
settings-frame

[dpapad, 2017/03/04 02:54:05]

SGTM. I did not know we can filter by URL.

+    });
     // Preload bold Roboto so it doesn't load and flicker the first time used.
     document.fonts.load('bold 12px Roboto');
     settings.setGlobalScrollTarget(this.$.headerPanel.scroller);
   },
 
   /** @override */
   detached: function() {
     settings.resetRouteForTesting();
   },
 
@@ skipping 62 matching lines @@
   onMenuButtonTap_: function() {
     this.$.drawer.toggle();
   },
 
   /** @private */
   directionDelegateChanged_: function() {
     this.$.drawer.align = this.directionDelegate.isRtl() ?
         'right' : 'left';
   },
 });