Add UMA metrics for profile switching.

chrome/browser/browser_shutdown.cc

Index: chrome/browser/browser_shutdown.cc
diff --git a/chrome/browser/browser_shutdown.cc b/chrome/browser/browser_shutdown.cc
index 9761f06fd6545b2c212309bb2a39abcd6b3bb119..8974bd502d5ddcaa8cd004f7418bd55389d74b6b 100644
--- a/chrome/browser/browser_shutdown.cc
+++ b/chrome/browser/browser_shutdown.cc
@@ -24,6 +24,7 @@
 #include "chrome/browser/first_run/upgrade_util.h"
 #include "chrome/browser/lifetime/application_lifetime.h"
 #include "chrome/browser/profiles/profile_manager.h"
+#include "chrome/browser/profiles/profile_metrics.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/crash_keys.h"
@@ -153,6 +154,9 @@ bool ShutdownPreThreadsStop() {
   // consider putting it in BrowserProcessImpl::EndSession.
   PrefService* prefs = g_browser_process->local_state();
 
+  // Log the amount of times the user switched profiles during this session.
+  ProfileMetrics::LogNumberOfProfileSwitches();
+
   metrics::MetricsService* metrics = g_browser_process->metrics_service();
   if (metrics)
     metrics->RecordCompletedSessionEnd();