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

ash/wm/root_window_layout_manager.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/wm/root_window_layout_manager.h"
 
 #include "ui/aura/window.h"
 #include "ui/compositor/layer.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace internal {
 
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowLayoutManager, public:
 
 RootWindowLayoutManager::RootWindowLayoutManager(aura::Window* owner)
-    : owner_(owner),
-      background_widget_(NULL) {
+    : owner_(owner) {
+  for (int i = 0; i < kShellWindowCount; i++)
+    background_widget_[i] = NULL;
 }
 
 RootWindowLayoutManager::~RootWindowLayoutManager() {
 }
 
-void RootWindowLayoutManager::SetBackgroundWidget(views::Widget* widget) {
-  if (widget == background_widget_)
+void RootWindowLayoutManager::SetBackgroundWidget(views::Widget* widget,
+    int container_id) {
+  if (widget == background_widget_[container_id])
     return;
   // Close now so that the focus manager will be deleted before shutdown.
-  if (background_widget_)
-    background_widget_->CloseNow();
-  background_widget_ = widget;
+  if (background_widget_[container_id])
+    background_widget_[container_id]->CloseNow();
+  background_widget_[container_id] = widget;
 }
 
-void RootWindowLayoutManager::SetBackgroundLayer(ui::Layer* layer) {
-  background_layer_.reset(layer);
+void RootWindowLayoutManager::SetBackgroundLayer(ui::Layer* layer,
+    int container_id) {
+  background_layer_[container_id].reset(layer);
+}
+
+void RootWindowLayoutManager::DropBackgroundForContainer(int container_id) {
+  SetBackgroundLayer(NULL, container_id);
+  SetBackgroundWidget(NULL, container_id);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowLayoutManager, aura::LayoutManager implementation:
 
 void RootWindowLayoutManager::OnWindowResized() {
   gfx::Rect fullscreen_bounds =
       gfx::Rect(owner_->bounds().width(), owner_->bounds().height());
 
   // Resize both our immediate children (the containers-of-containers animated
   // by PowerButtonController) and their children (the actual containers).
   aura::Window::Windows::const_iterator i;
   for (i = owner_->children().begin(); i != owner_->children().end(); ++i) {
     (*i)->SetBounds(fullscreen_bounds);
     aura::Window::Windows::const_iterator j;
     for (j = (*i)->children().begin(); j != (*i)->children().end(); ++j)
       (*j)->SetBounds(fullscreen_bounds);
   }
-
-  if (background_widget_)
-    background_widget_->SetBounds(fullscreen_bounds);
-  if (background_layer_.get())
-    background_layer_->SetBounds(fullscreen_bounds);
+  for (int i = 0; i < kShellWindowCount; i++) {
+    if (background_widget_[i])
+      background_widget_[i]->SetBounds(fullscreen_bounds);
+    if (background_layer_[i].get())
+      background_layer_[i]->SetBounds(fullscreen_bounds);
+  }
 }
 
 void RootWindowLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
 }
 
 void RootWindowLayoutManager::OnWillRemoveWindowFromLayout(
     aura::Window* child) {
 }
 
 void RootWindowLayoutManager::OnWindowRemovedFromLayout(aura::Window* child) {
 }
 
 void RootWindowLayoutManager::OnChildWindowVisibilityChanged(
     aura::Window* child,
     bool visible) {
 }
 
 void RootWindowLayoutManager::SetChildBounds(
     aura::Window* child,
     const gfx::Rect& requested_bounds) {
   SetChildBoundsDirect(child, requested_bounds);
 }
 
 }  // namespace internal
 }  // namespace ash