We seem to have a similar failure on PageLoadMetricsBrowserTest.NoStatePrefetchObserverCacheable with

Histogram "Prerender.none_NoStatePrefetchTTFCP.Reference.Cacheable" does not exist.

Raising to Pri-1 as this is creating noise on the bots.

Bot output here:

https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/47071

Linux ChromiumOS Tests is passing reliably...
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%281%29?numbuilds=200

...but this flake is still happening:
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%281%29/builds/27387/steps/browser_tests%20on%20Ubuntu-12.04/logs/stdio

Here, for instance, PageLoadMetricsBrowserTest.FirstMeaningfulPaintNotRecorded failed twice before succeeding on the second retry.

I created a separate bug for PageLoadMetricsBrowserTest.NoStatePrefetchObserverCacheable:  Issue 657022 .

This failure just re-occured: https://uberchromegw.corp.google.com/i/chromium.linux/builders/Linux%20Tests/builds/54420

ksakamoto@, can you take a look or route this to someone else please?

ksakamoto, note that this most recent flake occurred with browser-side navigation enabled. To repro you'll want to include --enable-browser-side-navigation on the command line.

Sorry for the lack of activity.
Created a patch: https://codereview.chromium.org/2799423002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/115a1494e75fec1c214329b8e8f0be9b35194785

commit 115a1494e75fec1c214329b8e8f0be9b35194785
Author: ksakamoto <ksakamoto@chromium.org>
Date: Mon Apr 10 02:13:12 2017

Deflake PageLoadMetricsBrowserTest.FirstMeaningfulPaintNotRecorded

There are two causes of flakiness:

1. ui_test_utils::NavigateToURL() does not guarantee that the page had
   a paint after the navigation. FirstMeaningfulPaintStatus will not be
   logged if the page is not painted at all. This patch adds a FCP
   observer to prevent this.

2. The page may reach network-idle and report FirstMeaningfulPaint
   before the tester calls NavigateToUntrackedUrl(). To prevent this,
   this patch adds some slow fetch() requests in the test page.

BUG= 651870 

Review-Url: https://codereview.chromium.org/2799423002
Cr-Commit-Position: refs/heads/master@{#463165}

[modify] https://crrev.com/115a1494e75fec1c214329b8e8f0be9b35194785/chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc
[add] https://crrev.com/115a1494e75fec1c214329b8e8f0be9b35194785/chrome/test/data/page_load_metrics/page_with_active_connections.html