Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

chrome/browser/ui/views/frame/browser_view.cc

Index: chrome/browser/ui/views/frame/browser_view.cc
diff --git a/chrome/browser/ui/views/frame/browser_view.cc b/chrome/browser/ui/views/frame/browser_view.cc
index a1cbb838069202e58a1b5d0eff4b9434f89e5707..162200166eddbae8b07701dd2576cd3e5ce31547 100644
--- a/chrome/browser/ui/views/frame/browser_view.cc
+++ b/chrome/browser/ui/views/frame/browser_view.cc
@@ -419,8 +419,7 @@ BrowserView::BrowserView()
       handling_theme_changed_(false),
       in_process_fullscreen_(false),
       force_location_bar_focus_(false),
-      activate_modal_dialog_factory_(this) {
-}
+      activate_modal_dialog_factory_(this) {}
 
 BrowserView::~BrowserView() {
   // All the tabs should have been destroyed already. If we were closed by the
@@ -2000,6 +1999,14 @@ void BrowserView::ViewHierarchyChanged(
   }
 }
 
+void BrowserView::PaintChildren(const ui::PaintContext& context) {
+  views::ClientView::PaintChildren(context);
+  // Don't reset the instance before it had a chance to get compositor callback.
+  if (!histogram_helper_.get())

[Alexei Svitkine (slow), 2017/04/18 16:01:32]

Nit: {}

Also, does if (!histogram_helper_) work? (without the .get())

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

sky prefers the absence of curly brackets on single-line expressions :-)

Yes, it works without .get(), but I thought that it added more clarity.

I don't have a strong position here, so I yielded in both cases.

+    histogram_helper_ = BrowserWindowHistogramHelper::OnBrowserPainted(
+        GetWidget()->GetCompositor());
+}
+
 void BrowserView::ChildPreferredSizeChanged(View* child) {
   Layout();
 }