Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

chrome/browser/metrics/startup_metrics_browsertest.cc

+// Copyright 2017 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 <set>
+
+#include "base/metrics/histogram_samples.h"
+#include "base/metrics/statistics_recorder.h"
+#include "base/run_loop.h"
+#include "chrome/test/base/in_process_browser_test.h"
+
+using StartupMetricsTest = InProcessBrowserTest;
+
+namespace {
+
+constexpr const char* kStartupMetrics[] = {
+    "Startup.BrowserWindow.FirstPaint",
+    "Startup.BrowserWindow.FirstPaint.CompositingEnded",
+};

[gab, 2017/04/18 13:52:15]

List all metrics in startup_metrics_utils.cc:

constexpr const char* kStartupMetrics[] = {
    "Startup.BrowserMainToRendererMain",
    "Startup.BrowserMessageLoopStartTime",
    "Startup.BrowserMessageLoopStartTimeFromMainEntry2",
    "Startup.BrowserOpenTabs",
    "Startup.BrowserWindow.FirstPaint",
    "Startup.BrowserWindow.FirstPaint.CompositingEnded",
    "Startup.BrowserWindowDisplay",
    "Startup.FirstWebContents.MainFrameLoad2",
    "Startup.FirstWebContents.MainNavigationFinished",
    "Startup.FirstWebContents.MainNavigationStart",
    "Startup.FirstWebContents.NonEmptyPaint2",
    "Startup.LoadTime.ExeMainToDllMain2",
    "Startup.LoadTime.ProcessCreateToDllMain2",
    "Startup.LoadTime.ProcessCreateToExeMain2",
    "Startup.SystemUptime",
#if defined(OS_WIN)
    "Startup.BrowserMessageLoopStartHardFaultCount",
    "Startup.Temperature",
#endif  // defined(OS_WIN)
};

[themblsha, 2017/04/19 15:06:09]

Done.

+
+}  // namespace
+
+// RecordBrowserWindowFirstPaint and
+// RecordBrowserWindowFirstPaintCompositingEnded have a static variables inside,
+// so we can't run several tests inside a single process, and thus this test
+// cannot be in unit_tests.

[gab, 2017/04/18 13:52:15]

Remove this paragraph (it's obvious now why it's an integration test)

[themblsha, 2017/04/19 15:06:09]

Done.

+
+// Tests that the specified startup-specific histograms are indeed reported.

[gab, 2017/04/18 13:52:15]

Change to:

// Verify that startup histograms are logged on browser startup.

[themblsha, 2017/04/19 15:06:09]

Done.

+IN_PROC_BROWSER_TEST_F(StartupMetricsTest, ReportsValues) {
+  for (auto* const histogram : kStartupMetrics) {
+    while (!base::StatisticsRecorder::FindHistogram(histogram))
+      base::RunLoop().RunUntilIdle();
+  }
+}