Separate the logic of popup alignment and workarea handling as delegate.

chrome/browser/ui/views/message_center/web_notification_tray.cc

Index: chrome/browser/ui/views/message_center/web_notification_tray.cc
diff --git a/chrome/browser/ui/views/message_center/web_notification_tray.cc b/chrome/browser/ui/views/message_center/web_notification_tray.cc
index c28f2bef3de7603b2fbe5f7303d48d6ea97696a9..473468cffe7f5c5049a5c9f91c0c34dd731ab459 100644
--- a/chrome/browser/ui/views/message_center/web_notification_tray.cc
+++ b/chrome/browser/ui/views/message_center/web_notification_tray.cc
@@ -27,6 +27,7 @@
 #include "ui/gfx/size.h"
 #include "ui/message_center/message_center_tray.h"
 #include "ui/message_center/message_center_tray_delegate.h"
+#include "ui/message_center/views/desktop_popup_alignment_delegate.h"
 #include "ui/message_center/views/message_popup_collection.h"
 #include "ui/views/widget/widget.h"
 
@@ -135,8 +136,10 @@ WebNotificationTray::WebNotificationTray(PrefService* local_state)
   message_center_tray_.reset(
       new MessageCenterTray(this, g_browser_process->message_center()));
   last_quiet_mode_state_ = message_center()->IsQuietMode();
+  alignment_delegate_.reset(new message_center::DesktopPopupAlignmentDelegate);
   popup_collection_.reset(new message_center::MessagePopupCollection(
-      NULL, message_center(), message_center_tray_.get(), false));
+      NULL, message_center(), message_center_tray_.get(),
+      alignment_delegate_.get()));
 
 #if defined(OS_WIN)
   // |local_state| can be NULL in tests.
@@ -164,6 +167,7 @@ message_center::MessageCenter* WebNotificationTray::message_center() {
 }
 
 bool WebNotificationTray::ShowPopups() {
+  alignment_delegate_->StartObserving(gfx::Screen::GetNativeScreen());
   popup_collection_->DoUpdateIfPossible();
   return true;
 }