Added the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram to track time between tab swit

chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc

Index: chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
diff --git a/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc b/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
index 1b617147813255fcd5ccb26f3f04ae4c346c3996..7eb8da5b75b97e40a83e033853d684faa42d7c6b 100644
--- a/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
+++ b/chrome/browser/ui/ash/chrome_shell_delegate_chromeos.cc
@@ -217,10 +217,13 @@ void ChromeShellDelegate::PreInit() {
   // in Shell::Init.
   display_configuration_observer_.reset(
       new chromeos::DisplayConfigurationObserver());
+
+  chrome_user_metrics_recorder_.reset(new ChromeUserMetricsRecorder);
 }
 
 void ChromeShellDelegate::PreShutdown() {
   display_configuration_observer_.reset();
+  chrome_user_metrics_recorder_.reset();
 }
 
 ash::SessionStateDelegate* ChromeShellDelegate::CreateSessionStateDelegate() {