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

ash/wm/root_window_layout_manager.cc

Index: ash/wm/root_window_layout_manager.cc
diff --git a/ash/wm/root_window_layout_manager.cc b/ash/wm/root_window_layout_manager.cc
index 52c117e322a3f4b6285eef05326575ce8eb635f2..2b5df2f0714ecc9738cf39304340e4670c4612b7 100644
--- a/ash/wm/root_window_layout_manager.cc
+++ b/ash/wm/root_window_layout_manager.cc
@@ -4,6 +4,7 @@
 
 #include "ash/wm/root_window_layout_manager.h"
 
+#include "ash/desktop_background/desktop_background_widget_controller.h"
 #include "ui/aura/window.h"
 #include "ui/compositor/layer.h"
 #include "ui/views/widget/widget.h"
@@ -15,25 +16,12 @@ namespace internal {
 // RootWindowLayoutManager, public:
 
 RootWindowLayoutManager::RootWindowLayoutManager(aura::Window* owner)
-    : owner_(owner),
-      background_widget_(NULL) {
+    : owner_(owner) {
 }
 
 RootWindowLayoutManager::~RootWindowLayoutManager() {
 }
 
-void RootWindowLayoutManager::SetBackgroundWidget(views::Widget* widget) {
-  if (widget == background_widget_)
-    return;
-  // Close now so that the focus manager will be deleted before shutdown.
-  if (background_widget_)
-    background_widget_->CloseNow();
-  background_widget_ = widget;
-}
-
-void RootWindowLayoutManager::SetBackgroundLayer(ui::Layer* layer) {
-  background_layer_.reset(layer);
-}
 
 ////////////////////////////////////////////////////////////////////////////////
 // RootWindowLayoutManager, aura::LayoutManager implementation:
@@ -51,11 +39,10 @@ void RootWindowLayoutManager::OnWindowResized() {
     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);
+  internal::DesktopBackgroundWidgetController* background =
+      owner_->GetProperty(internal::kWindowDesktopComponent);
+  if (background)
+    background->SetBounds(fullscreen_bounds);
 }
 
 void RootWindowLayoutManager::OnWindowAddedToLayout(aura::Window* child) {