Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

chrome/browser/metrics/browser_view_histogram_helper.cc

Index: chrome/browser/metrics/browser_view_histogram_helper.cc
diff --git a/chrome/browser/metrics/browser_view_histogram_helper.cc b/chrome/browser/metrics/browser_view_histogram_helper.cc
new file mode 100644
index 0000000000000000000000000000000000000000..571280ac660bc4c3814b3d2b28e14e0c4b4671e5
--- /dev/null
+++ b/chrome/browser/metrics/browser_view_histogram_helper.cc
@@ -0,0 +1,54 @@
+// 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 "chrome/browser/metrics/browser_view_histogram_helper.h"
+
+#include "components/startup_metric_utils/browser/startup_metric_utils.h"
+#include "ui/compositor/compositor.h"
+
+BrowserViewHistogramHelper::BrowserViewHistogramHelper()
+    : scoped_observer_(this) {}
+
+BrowserViewHistogramHelper::~BrowserViewHistogramHelper() {}
+
+void BrowserViewHistogramHelper::OnBrowserPainted(ui::Compositor* compositor) {
+  if (did_first_paint_)
+    return;
+
+  did_first_paint_ = true;
+
+  startup_metric_utils::RecordBrowserViewFirstPaint(base::TimeTicks::Now());
+
+#if defined(OS_MACOSX)
+  if (!compositor) {
+    // In Cocoa version of Chromium UI is rendered inside the main process using
+    // CoreAnimation compositor, and at this point everything is already visible
+    // to the user.
+    startup_metric_utils::RecordBrowserViewFirstPaintCompositingEnded(
+        base::TimeTicks::Now());
+    return;
+  }
+#endif  // OS_MACOSX
+
+  scoped_observer_.Add(compositor);
+}
+
+void BrowserViewHistogramHelper::RemoveCompositorObserver() {
+  scoped_observer_.RemoveAll();
+}
+
+// OnCompositingEnded was removed crbug.com/671202, this is the next best thing.
+void BrowserViewHistogramHelper::OnCompositingStarted(
+    ui::Compositor* compositor,
+    base::TimeTicks start_time) {
+  startup_metric_utils::RecordBrowserViewFirstPaintCompositingEnded(
+      base::TimeTicks::Now());
+
+  RemoveCompositorObserver();
+}
+
+void BrowserViewHistogramHelper::OnCompositingShuttingDown(
+    ui::Compositor* compositor) {
+  RemoveCompositorObserver();
+}