Track adding a new user automatically.

When the last profile is deleted, a new one is created automatically.

BUG=410008

Review URL: https://codereview.chromium.org/532963004

Cr-Commit-Position: refs/heads/master@{#293497}

chrome/browser/profiles/profile_manager.cc

@@ -675,6 +675,9 @@ void ProfileManager::ScheduleProfileForDeletion(
                          new_profile_name,
                          new_avatar_url,
                          std::string());
+
+      ProfileMetrics::LogProfileAddNewUser(
+          ProfileMetrics::ADD_NEW_USER_LAST_DELETED);
     } else {
       // On the Mac, the browser process is not killed when all browser windows
       // are closed, so just in case we are deleting the active profile, and no

chrome/browser/profiles/profile_metrics.h

@@ -33,10 +33,11 @@ class ProfileMetrics {
 
   // Enum for counting the ways users were added.
   enum ProfileAdd {
-    ADD_NEW_USER_ICON = 0,    // User adds new user from icon menu
-    ADD_NEW_USER_MENU,        // User adds new user from menu bar
-    ADD_NEW_USER_DIALOG,      // User adds new user from create-profile dialog
-    ADD_NEW_USER_MANAGER,     // User adds new user from User Manager
+    ADD_NEW_USER_ICON = 0,      // User adds new user from icon menu
+    ADD_NEW_USER_MENU,          // User adds new user from menu bar
+    ADD_NEW_USER_DIALOG,        // User adds new user from create-profile dialog
+    ADD_NEW_USER_MANAGER,       // User adds new user from User Manager
+    ADD_NEW_USER_LAST_DELETED,  // Auto-created after deleting last user
     NUM_PROFILE_ADD_METRICS
   };
 

tools/metrics/histograms/histograms.xml

@@ -48149,6 +48149,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="Add new user from title bar menu"/>
   <int value="2" label="Add new user from settings dialog"/>
   <int value="3" label="Add new user from the User Manager"/>
+  <int value="4" label="Auto-created after deleting last user"/>
 </enum>
 
 <enum name="ProfileAndroidAccountManagementMenu" type="int">