2nd display should show the same background as login/lock screen:

ash/root_window_controller.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/root_window_controller.h"
 
 #include <vector>
 
 #include "ash/display/display_controller.h"
 #include "ash/shell.h"
@@ skipping 155 matching lines @@
       new internal::SystemModalContainerLayoutManager(modal_container));
   SetChildWindowVisibilityChangesAnimated(modal_container);
   SetUsesScreenCoordinates(modal_container);
 
   aura::Window* input_method_container = CreateContainer(
       internal::kShellWindowId_InputMethodContainer,
       "InputMethodContainer",
       non_lock_screen_containers);
   SetUsesScreenCoordinates(input_method_container);
 
+  aura::Window* lock_background_containers = CreateContainer(
+      internal::kShellWindowId_LockScreenBackgroundContainer,
+      "LockScreenBackgroundContainer",
+      lock_screen_containers);
+
+  SetChildWindowVisibilityChangesAnimated(lock_background_containers);
+
   // TODO(beng): Figure out if we can make this use
   // SystemModalContainerEventFilter instead of stops_event_propagation.
   aura::Window* lock_container = CreateContainer(
       internal::kShellWindowId_LockScreenContainer,
       "LockScreenContainer",
       lock_screen_containers);
   lock_container->SetLayoutManager(
       new internal::BaseLayoutManager(root_window));
   SetUsesScreenCoordinates(lock_container);
   // TODO(beng): stopsevents
@@ skipping 84 matching lines @@
       new internal::BaseLayoutManager(
           always_on_top_container->GetRootWindow()));
 }
 
 void RootWindowController::CreateContainers() {
   CreateContainersInRootWindow(root_window_.get());
 }
 
 void RootWindowController::CloseChildWindows() {
   // Close background widget first as it depends on tooltip.
-  root_window_layout_->SetBackgroundWidget(NULL);
+  root_window_layout_->SetBackgroundWidget(NULL,
+      kShellWindowId_DesktopBackgroundContainer);
   workspace_controller_.reset();
   aura::client::SetTooltipClient(root_window_.get(), NULL);
 
   while (!root_window_->children().empty()) {
     aura::Window* child = root_window_->children()[0];
     delete child;
   }
 }
 
 bool RootWindowController::IsInMaximizedMode() const {
@@ skipping 21 matching lines @@
   // Restore focused or active window if it's still alive.
   if (focused && tracker.Contains(focused) && dst->Contains(focused)) {
     dst->GetFocusManager()->SetFocusedWindow(focused, NULL);
   } else if (active && tracker.Contains(active) && dst->Contains(active)) {
     activation_client->ActivateWindow(active);
   }
 }
 
 }  // namespace internal
 }  // namespace ash