History: Add load-time metric for non-MD and MD History WebUI

chrome/browser/resources/md_history/history.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.
 
 // Send the history query immediately. This allows the query to process during
 // the initial page startup.
 chrome.send('queryHistory', ['', 0, 0, 0, RESULTS_PER_PAGE]);
 chrome.send('getForeignSessions');
 
 /** @type {Promise} */
 var upgradePromise = null;
+/** @type {boolean} */
+var resultsRendered = false;
 
 /**
  * @return {!Promise} Resolves once the history-app has been fully upgraded.
  */
 function waitForAppUpgrade() {
   if (!upgradePromise) {
     upgradePromise = new Promise(function(resolve, reject) {
       if (window.Polymer && Polymer.isInstance &&
           Polymer.isInstance($('history-app'))) {
         resolve();
       } else {
         $('bundle').addEventListener('load', resolve);
       }
     });
   }
   return upgradePromise;
 }
 
 // Chrome Callbacks-------------------------------------------------------------
 
 /**
  * Our history system calls this function with results from searches.
  * @param {HistoryQuery} info An object containing information about the query.
  * @param {!Array<HistoryEntry>} results A list of results.
  */
 function historyResult(info, results) {
   waitForAppUpgrade().then(function() {
     /** @type {HistoryAppElement} */($('history-app'))
         .historyResult(info, results);
-    // TODO(tsergeant): Showing everything as soon as the list is ready is not
-    // ideal, as the sidebar can still pop in after. Fix this to show everything
-    // at once.
     document.body.classList.remove('loading');
+
+    if (!resultsRendered) {
+      resultsRendered = true;
+      // requestAnimationFrame allows measurement immediately before the next
+      // repaint, but after the first page of <iron-list> items has stamped.
+      requestAnimationFrame(function() {
+        chrome.send(
+            'metricsHandler:recordTime',
+            ['History.ResultsRenderedTime', window.performance.now()]);
+      });
+    }
   });
 }
 
 /**
  * Called by the history backend after receiving results and after discovering
  * the existence of other forms of browsing history.
  * @param {boolean} hasSyncedResults Whether there are synced results.
  * @param {boolean} includeOtherFormsOfBrowsingHistory Whether to include
  *     a sentence about the existence of other forms of browsing history.
  */
@@ skipping 35 matching lines @@
 /**
  * Called by the history backend after user's sign in state changes.
  * @param {boolean} isUserSignedIn Whether user is signed in or not now.
  */
 function updateSignInState(isUserSignedIn) {
   waitForAppUpgrade().then(function() {
     /** @type {HistoryAppElement} */($('history-app'))
         .updateSignInState(isUserSignedIn);
   });
 }