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 c768ca57be3b83b79ee3ed09b1bdf10c5bb2157e..08612591e46d545a130578927a69f453a8fca657 100644
--- a/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
+++ b/chrome/browser/chromeos/chrome_browser_main_chromeos.cc
@@ -529,6 +529,9 @@ void ChromeBrowserMainPartsChromeos::PreProfileInit() {
                                   &tracker_);
 #endif
 
+  removable_device_notifications_ =
+      new RemovableDeviceNotificationsCros();
+
   // In Aura builds this will initialize ash::Shell.
   ChromeBrowserMainPartsLinux::PreProfileInit();
 }
@@ -596,8 +599,7 @@ 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