[Mac] Track when the User Manager is opened.

chrome/browser/ui/cocoa/profiles/user_manager_mac.mm

Index: chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
diff --git a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
index 957d95ba57bb6b8b04cab3e077f8fa47836a668c..3805e4b6b42f670710ca718e9592b3eedfafe23a 100644
--- a/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
+++ b/chrome/browser/ui/cocoa/profiles/user_manager_mac.mm
@@ -177,6 +177,7 @@ UserManagerMac::~UserManagerMac() {
 // static
 void UserManagerMac::Show(const base::FilePath& profile_path_to_focus,
                           profiles::UserManagerTutorialMode tutorial_mode) {
+  ProfileMetrics::LogProfileSwitchUser(ProfileMetrics::OPEN_USER_MANAGER);
   if (instance_) {
     // If there's a user manager window open already, just activate it.
     [instance_->window_controller_ show];