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

chrome/browser/resources/history/history.js

Index: chrome/browser/resources/history/history.js
diff --git a/chrome/browser/resources/history/history.js b/chrome/browser/resources/history/history.js
index 7643b8fd336866b834cfcf4ee793251c74102bde..b22f731a3cdabf1e3d4893e3e19c651d87a166ac 100644
--- a/chrome/browser/resources/history/history.js
+++ b/chrome/browser/resources/history/history.js
@@ -75,6 +75,14 @@ function recordUmaHistogram(histogram, maxBucketValue, value) {
               maxBucketValue]);
 }
 
+/**
+ * Record the current time in milliseconds since pageload into a UMA histogram.
+ * @param {string} histogram The name of the histogram to be recorded in.
+ */
+function recordTimeHistogram(histogram) {

[calamity, 2016/08/03 08:23:22]

Is this worth moving into cr_util.js?

[calamity, 2016/08/03 08:23:22]

Param no longer needed?

[Dan Beam, 2016/08/03 21:05:17]

why not just inline this method?  it's only used once

[tsergeant, 2016/08/03 22:53:56]

Sure, inlined.

+  chrome.send('metricsHandler:recordTime', [histogram, performance.now()]);
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Visit:
 
@@ -939,6 +947,7 @@ function HistoryView(model) {
   this.model_ = model;
   this.pageIndex_ = 0;
   this.lastDisplayed_ = [];
+  this.hasRenderedResults_ = false;
 
   this.model_.setView(this);
 
@@ -1122,6 +1131,13 @@ HistoryView.prototype.onModelReady = function(doneLoading) {
     var isSearch = this.model_.getSearchText().length > 0;
     $('search-field').hidden = !(hasResults || isSearch);
   }
+
+  if (!this.hasRenderedResults_) {
+    this.hasRenderedResults_ = true;
+    requestAnimationFrame(function() {

[tsergeant, 2016/08/03 07:37:04]

I have two main options here:

* requestAnimationFrame, which will always fire just before the next repaint.
That means it doesn't take into account the time taken for paint itself.

* setTimeout 0, which seems to be -after- the next paint but before the
iron-list renders more items. However, I'm really not sure what kind of
guarantees there are on this -- particularly since the rest of the iron-list
rendering is also scheduled with setTimeout.

I've gone with rAF, since it's the one which I'm more certain about. WDYT?

[calamity, 2016/08/03 08:23:23]

rAF sgtm.

+      recordTimeHistogram('History.ResultsRenderedTime');
+    });
+  }
 };
 
 /**