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.BrowserMainToRendererMain",
+    "Startup.BrowserOpenTabs",
+    "Startup.BrowserWindow.FirstPaint",
+    "Startup.BrowserWindow.FirstPaint.CompositingEnded",
+    "Startup.BrowserWindowDisplay",
+    "Startup.FirstWebContents.MainFrameLoad2",
+    "Startup.FirstWebContents.MainNavigationFinished",
+    "Startup.FirstWebContents.MainNavigationStart",
+    "Startup.FirstWebContents.NonEmptyPaint2",
+
+// These histograms rely on normal browser startup through BrowserMain,
+// which calls BrowserMainRunnerImpl, which calls ChromeBrowserMainParts
+// which reports these metrics.
+// Currently they're not reported at all during browser_tests.

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

Should I create a new crbug for this? Fixing this in current CL seems to be out
of scope.

[gab, 2017/04/19 18:45:43]

Ah, right, let's not bother. Leaving them commented out here is fine, make the
above comments something like:

// The following histograms depend on normal browser startup through BrowserMain
// and are as such not caught by this browser test.

[themblsha, 2017/04/20 10:42:23]

Done.

Startup.BrowserMessageLoopStartHardFaultCount / Startup.Temperature could also
be BrowserMainRunnerImpl-dependent (I was testing locally on MacViews), if so
I'll comment them out as well.

+
+// "Startup.BrowserMessageLoopStartTime",
+// "Startup.BrowserMessageLoopStartTimeFromMainEntry2",
+// "Startup.LoadTime.ExeMainToDllMain2",
+// "Startup.LoadTime.ProcessCreateToDllMain2",
+// "Startup.LoadTime.ProcessCreateToExeMain2",
+// "Startup.SystemUptime",
+
+#if defined(OS_WIN)
+    "Startup.BrowserMessageLoopStartHardFaultCount",
+    "Startup.Temperature",
+#endif  // defined(OS_WIN)
+};
+
+}  // namespace
+
+// Verify that startup histograms are logged on browser startup.
+IN_PROC_BROWSER_TEST_F(StartupMetricsTest, ReportsValues) {
+  for (auto* const histogram : kStartupMetrics) {
+    while (!base::StatisticsRecorder::FindHistogram(histogram))
+      base::RunLoop().RunUntilIdle();
+  }
+}