Add Startup.BrowserView.FirstPaint / .CompositingEnded histograms.

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

Index: chrome/browser/ui/views/frame/browser_view.h
diff --git a/chrome/browser/ui/views/frame/browser_view.h b/chrome/browser/ui/views/frame/browser_view.h
index d2172e5a99568b3a15133d6c131f8eb2134b1f07..26debb71cd7e17b2699a146d0b844fb4ae2ef706 100644
--- a/chrome/browser/ui/views/frame/browser_view.h
+++ b/chrome/browser/ui/views/frame/browser_view.h
@@ -20,6 +20,7 @@
 #include "chrome/browser/extensions/extension_commands_global_registry.h"
 #include "chrome/browser/extensions/extension_keybinding_registry.h"
 #include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_view_histogram_helper.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/exclusive_access/exclusive_access_context.h"
 #include "chrome/browser/ui/infobar_container_delegate.h"
@@ -438,6 +439,7 @@ class BrowserView : public BrowserWindow,
   void OnGestureEvent(ui::GestureEvent* event) override;
   void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) override;
+  void PaintChildren(const ui::PaintContext& context) override;
   void ChildPreferredSizeChanged(View* child) override;
   void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
   void OnThemeChanged() override;
@@ -714,6 +716,8 @@ class BrowserView : public BrowserWindow,
   std::unique_ptr<ExtensionKeybindingRegistryViews>
       extension_keybinding_registry_;
 
+  BrowserViewHistogramHelper histogram_helper_;

[sky, 2017/04/11 17:13:36]

Why do you need BrowserViewHistogramHelper per browser? From the description of
the metrics it seems like we only need to record the histograms once, in which
case this should be global. Am I missing something?

[themblsha, 2017/04/12 17:18:29]

It's placed here as an instance variable so it could wait for the first
Compositor operation after the Browser UI was painted. Should I create a proper
singleton instance instead?

[sky, 2017/04/12 19:34:08]

How about calling a factory function for creation that internally maintains if
the first logging happened. If it happened, null is returned.

[themblsha, 2017/04/17 17:34:49]

Done.

+
   mutable base::WeakPtrFactory<BrowserView> activate_modal_dialog_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserView);