GTK: Add TRACE_EVENTs around gtk ui events.

chrome/browser/ui/gtk/infobars/infobar_gtk.cc

Index: chrome/browser/ui/gtk/infobars/infobar_gtk.cc
diff --git a/chrome/browser/ui/gtk/infobars/infobar_gtk.cc b/chrome/browser/ui/gtk/infobars/infobar_gtk.cc
index eb22a332080853e6a988215bd8ad7a2c5a8130f2..57bd1ea8079654a64e4dc6e3776c0ed8e713a692 100644
--- a/chrome/browser/ui/gtk/infobars/infobar_gtk.cc
+++ b/chrome/browser/ui/gtk/infobars/infobar_gtk.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/ui/gtk/infobars/infobar_gtk.h"
 
+#include "base/debug/trace_event.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/infobars/infobar_tab_helper.h"
 #include "chrome/browser/profiles/profile.h"
@@ -212,6 +213,8 @@ void InfoBarGtk::OnCloseButton(GtkWidget* button) {
 
 gboolean InfoBarGtk::OnBackgroundExpose(GtkWidget* sender,
                                         GdkEventExpose* event) {
+  TRACE_EVENT0("ui::gtk", "InfoBarGtk::OnBackgroundExpose");
+
   const int height = sender->allocation.height;
 
   cairo_t* cr = gdk_cairo_create(GDK_DRAWABLE(sender->window));