Make UserActivityDetector a singleton

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

Index: chrome/browser/chromeos/chrome_browser_main_chromeos.cc
diff --git a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
index 0139f77c113d758effb068824383adc4a3725626..0b99d2666824e8417286a58a482d8052cff4ee5c 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
@@ -117,6 +117,7 @@
 #include "net/url_request/url_request_context_getter.h"
 #include "ui/base/touch/touch_device.h"
 #include "ui/events/event_utils.h"
+#include "ui/wm/core/user_activity_detector.h"
 
 // Exclude X11 dependents for ozone
 #if defined(USE_X11)
@@ -401,6 +402,9 @@ void ChromeBrowserMainPartsChromeos::PreProfileInit() {
         new default_app_order::ExternalLoader(true /* async */));
   }
 
+  // Initialize the UserActivityDetector before the ash Shell is created.
+  wm::UserActivityDetector::Create();
+
   media::SoundsManager::Create();
 
   // Initialize magnification manager before ash tray is created. And this must
@@ -734,6 +738,8 @@ void ChromeBrowserMainPartsChromeos::PostMainMessageLoopRun() {
 
   media::SoundsManager::Shutdown();
 
+  wm::UserActivityDetector::Shutdown();
+
   system::StatisticsProvider::GetInstance()->Shutdown();
 
   // Let the UserManager and WallpaperManager unregister itself as an observer