Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

chrome/browser/ui/views/frame/browser_view_histogram_helper_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 "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"
+
+namespace {
+
+const char kStartupBrowserViewFirstPaintHistogramName[] =
+    "Startup.BrowserView.FirstPaint";
+const char kStartupBrowserViewFirstPaintCompositingEndedHistogramName[] =
+    "Startup.BrowserView.FirstPaint.CompositingEnded";
+
+}  // namespace
+
+using BrowserViewHistogramHelperTest = InProcessBrowserTest;
+
+// RecordBrowserViewFirstPaint and RecordBrowserViewFirstPaintCompositingEnded
+// have a static variables inside, so we can't run several tests inside a single
+// process, and thus these tests cannot be unit_tests.
+
+IN_PROC_BROWSER_TEST_F(BrowserViewHistogramHelperTest, FirstPaint) {
+  base::HistogramBase* histogram = nullptr;
+  while (!histogram) {
+    histogram = base::StatisticsRecorder::FindHistogram(
+        kStartupBrowserViewFirstPaintHistogramName);
+    base::RunLoop().RunUntilIdle();
+  }
+  EXPECT_EQ(1, histogram->SnapshotSamples()->TotalCount());
+}
+
+IN_PROC_BROWSER_TEST_F(BrowserViewHistogramHelperTest,
+                       FirstPaintCompositingEnded) {
+  base::HistogramBase* histogram = nullptr;
+  while (!histogram) {
+    histogram = base::StatisticsRecorder::FindHistogram(
+        kStartupBrowserViewFirstPaintCompositingEndedHistogramName);
+    base::RunLoop().RunUntilIdle();
+  }
+  EXPECT_EQ(1, histogram->SnapshotSamples()->TotalCount());
+}