Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

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

 // Copyright 2012 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/ui/views/frame/browser_view.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <memory>
@@ skipping 401 matching lines @@
       toolbar_(nullptr),
       find_bar_host_view_(nullptr),
       infobar_container_(nullptr),
       contents_web_view_(nullptr),
       devtools_web_view_(nullptr),
       contents_container_(nullptr),
       initialized_(false),
       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
   // OS with some tabs than the NativeBrowserFrame should have destroyed them.
   DCHECK_EQ(0, browser_->tab_strip_model()->count());
 
   // Stop the animation timer explicitly here to avoid running it in a nested
   // message loop, which may run by Browser destructor.
   loading_animation_timer_.Stop();
 
@@ skipping 1559 matching lines @@
 }
 
 void BrowserView::ViewHierarchyChanged(
     const ViewHierarchyChangedDetails& details) {
   if (!initialized_ && details.is_add && details.child == this && GetWidget()) {
     InitViews();
     initialized_ = true;
   }
 }
 
+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();
 }
 
 void BrowserView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
   node_data->role = ui::AX_ROLE_CLIENT;
 }
 
 void BrowserView::OnThemeChanged() {
   if (!IsRegularOrGuestSession()) {
@@ skipping 677 matching lines @@
 }
 
 extensions::ActiveTabPermissionGranter*
 BrowserView::GetActiveTabPermissionGranter() {
   content::WebContents* web_contents = GetActiveWebContents();
   if (!web_contents)
     return nullptr;
   return extensions::TabHelper::FromWebContents(web_contents)
       ->active_tab_permission_granter();
 }