Layout login/lock screen, shelf and app list inside the first display in Unified Desktop mode

ash/display/display_controller.cc

Index: ash/display/display_controller.cc
diff --git a/ash/display/display_controller.cc b/ash/display/display_controller.cc
index 4044fe76464973527bd587b74faa68f5f90330be..e28472e09f3fe91ec454f2b230fb52236df36750 100644
--- a/ash/display/display_controller.cc
+++ b/ash/display/display_controller.cc
@@ -22,6 +22,7 @@
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/shell_delegate.h"
+#include "ash/system/tray/system_tray.h"
 #include "ash/wm/coordinate_conversion.h"
 #include "base/command_line.h"
 #include "base/stl_util.h"
@@ -643,6 +644,19 @@ void DisplayController::OnDisplayAdded(const gfx::Display& display) {
     if (primary_tree_host_for_replace_) {
       AshWindowTreeHost* to_delete = primary_tree_host_for_replace_;
       primary_tree_host_for_replace_ = nullptr;
+
+      // Show the shelf if the original WTH had a visible system
+      // tray. It may or may not be visible depending on OOBE state.
+      ash::SystemTray* old_tray =
+          GetRootWindowController(to_delete->AsWindowTreeHost()->window())
+              ->GetSystemTray();
+      ash::SystemTray* new_tray =
+          ash::Shell::GetInstance()->GetPrimarySystemTray();
+      if (old_tray->GetWidget()->IsVisible()) {
+        new_tray->SetVisible(true);
+        new_tray->GetWidget()->Show();
+      }
+

[Jun Mukai, 2015/05/01 22:14:45]

Is this necessary?  In the extended desktop mode, display changes
(adding/removing displays) closes the system tray bubble.

[oshima, 2015/05/01 23:44:52]

I'm showing the tray itself when necessary. It's hidden in login screen unless
explicitly shown.

[Jun Mukai, 2015/05/02 03:41:28]

Okay.  I was confused by the bubble visibility and tray widget visibility.

       DeleteHost(to_delete);
 #ifndef NDEBUG
       auto iter = std::find_if(