Regularize ownerships and lifecycle for storage monitor platform classes.

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 adf7e88c6eab5b0d440c41634eefdb9ce8e7bdcd..0674667dd0baaa4334b724dfbf4161f8414aed41 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
@@ -545,6 +545,9 @@ void ChromeBrowserMainPartsChromeos::PreProfileInit() {
                                   &tracker_);
 #endif
 
+  removable_device_notifications_ =
+      new RemovableDeviceNotificationsCros();
+
   // In Aura builds this will initialize ash::Shell.
   ChromeBrowserMainPartsLinux::PreProfileInit();
 }
@@ -620,8 +623,7 @@ void ChromeBrowserMainPartsChromeos::PostProfileInit() {
   }
   chromeos::accessibility::Initialize();
 
-  removable_device_notifications_ =
-      new RemovableDeviceNotificationsCros();
+  removable_device_notifications_->Init();
 
   // Initialize the network portal detector for Chrome OS. The network
   // portal detector starts to listen for notifications from