Prerender: Add FCP histograms to nostate browsertests.

chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc

 // Copyright (c) 2012 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/command_line.h"
 #include "base/strings/string16.h"
 #include "base/strings/string_split.h"
 #include "base/task_scheduler/post_task.h"
 #include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_manager.h"
@@ skipping 111 matching lines @@
   std::unique_ptr<TestPrerender> test_prerender =
       PrefetchFromFile(kPrefetchPage, FINAL_STATUS_NOSTATE_PREFETCH_FINISHED);
   main_counter.WaitForCount(1);
   script_counter.WaitForCount(1);
   script2_counter.WaitForCount(0);
 
   // Verify that the page load did not happen.
   test_prerender->WaitForLoads(0);
 }
 
+// Check that a prefetch followed by a load produces the approriate
+// histograms. Note that other histogram testing is done in
+// browser/page_load_metrics, in particular, testing the combinations of
+// Warm/Cold and Cacheable/NoCacheable.
+IN_PROC_BROWSER_TEST_F(NoStatePrefetchBrowserTest, PrefetchHistograms) {
+  RequestCounter main_counter;
+  CountRequestFor(kPrefetchPage, &main_counter);
+  RequestCounter script_counter;
+  CountRequestFor(kPrefetchScript, &script_counter);
+
+  PrefetchFromFile(kPrefetchPage, FINAL_STATUS_NOSTATE_PREFETCH_FINISHED);

[pasko, 2016/11/18 15:56:56]

PrefetchFromFile waits for Stop (i.e. when all prefetch requests are already
made), so request counters are not needed.

[mattcary, 2016/11/18 16:13:28]

Done.

+  main_counter.WaitForCount(1);
+  script_counter.WaitForCount(1);
+  histogram_tester().ExpectTotalCount(
+      "Prerender.websame_NoStatePrefetchTTFCP.Warm", 0);
+
+  test_utils::FirstContentfulPaintManagerWaiter* fcp_waiter =
+      test_utils::FirstContentfulPaintManagerWaiter::Create(
+          GetPrerenderManager());
+  ui_test_utils::NavigateToURL(
+      current_browser(), src_server()->GetURL(MakeAbsolute(kPrefetchPage)));
+  fcp_waiter->Wait();
+
+  histogram_tester().ExpectTotalCount(
+      "Prerender.websame_NoStatePrefetchTTFCP.Warm.Cacheable", 1);
+  histogram_tester().ExpectTotalCount(
+      "Prerender.websame_NoStatePrefetchResponseTypes", 2);
+}
+
 // Checks the prefetch of an img tag.
 IN_PROC_BROWSER_TEST_F(NoStatePrefetchBrowserTest, PrefetchImage) {
   RequestCounter image_counter;
   CountRequestFor(kPrefetchJpeg, &image_counter);
   base::StringPairs replacement_text;
   replacement_text.push_back(
       std::make_pair("REPLACE_WITH_IMAGE_URL", MakeAbsolute(kPrefetchJpeg)));
   std::string main_page_path;
   net::test_server::GetFilePathWithReplacements(
       kPrefetchImagePage, replacement_text, &main_page_path);
@@ skipping 243 matching lines @@
   // special way.
   // TODO(mattcary): since the prerender will count itself as loaded even if the
   // fetch of the main resource fails, the test doesn't actually confirm what we
   // want it to confirm. This may be fixed by planned changes to the prerender
   // lifecycle.
   std::unique_ptr<TestPrerender> prerender =
       PrefetchFromFile(kPrefetchPage, FINAL_STATUS_SAFE_BROWSING);
 }
 
 }  // namespace prerender