[NoStatePrefetch] Add performance histograms.

chrome/browser/page_load_metrics/page_load_metrics_browsertest.cc

 // Copyright (c) 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.
 
 #include "base/macros.h"
 #include "base/test/histogram_tester.h"
+#include "base/time/time.h"
 #include "chrome/browser/page_load_metrics/metrics_web_contents_observer.h"
 #include "chrome/browser/page_load_metrics/observers/aborts_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/core_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/document_write_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/no_state_prefetch_page_load_metrics_observer.h"
+#include "chrome/browser/prerender/prerender_histograms.h"
+#include "chrome/browser/prerender/prerender_origin.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_navigator_params.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/test/browser_test_utils.h"
 #include "net/test/embedded_test_server/embedded_test_server.h"
 
 class MetricsWebContentsObserverBrowserTest : public InProcessBrowserTest {
@@ skipping 399 matching lines @@
   NavigateToUntrackedUrl();
 
   histogram_tester_.ExpectUniqueSample(
       internal::kHistogramFirstMeaningfulPaintStatus,
       internal::FIRST_MEANINGFUL_PAINT_DID_NOT_REACH_NETWORK_STABLE, 1);
   histogram_tester_.ExpectTotalCount(
       internal::kHistogramFirstMeaningfulPaint, 0);
   histogram_tester_.ExpectTotalCount(
       internal::kHistogramParseStartToFirstMeaningfulPaint, 0);
 }
+
+IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest,

[Bryan McQuade, 2016/09/19 16:35:02]

i just landed a change that renamed these tests to PageLoadMetricsBrowserTest -
you'll need to rebase and then rename your tests to match, thanks!

+                       NoStatePrefetchObserverCacheable) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  ui_test_utils::NavigateToURL(browser(),
+                               embedded_test_server()->GetURL("/title1.html"));
+  NavigateToUntrackedUrl();
+
+  histogram_tester_.ExpectTotalCount(

[Bryan McQuade, 2016/09/19 16:35:02]

for completeness, can we also verify that the count for the no-store variant is
zero here?

+      prerender::PrerenderHistograms::GetFirstContentfulPaintHistogrameName(
+          prerender::ORIGIN_NONE, false, false, base::TimeDelta()),
+      1);
+}
+
+IN_PROC_BROWSER_TEST_F(MetricsWebContentsObserverBrowserTest,
+                       NoStatePrefetchObserverNoStore) {
+  ASSERT_TRUE(embedded_test_server()->Start());
+
+  ui_test_utils::NavigateToURL(browser(),
+                               embedded_test_server()->GetURL("/nostore.html"));
+  NavigateToUntrackedUrl();
+
+  histogram_tester_.ExpectTotalCount(

[Bryan McQuade, 2016/09/19 16:35:02]

likewise, let's verify that the non-no-store variant has a count of zero here.

+      prerender::PrerenderHistograms::GetFirstContentfulPaintHistogrameName(
+          prerender::ORIGIN_NONE, false, true, base::TimeDelta()),
+      1);
+}