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

ash/desktop_background/desktop_background_widget_controller.cc

Index: ash/desktop_background/desktop_background_widget_controller.cc
diff --git a/ash/desktop_background/desktop_background_widget_controller.cc b/ash/desktop_background/desktop_background_widget_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..12110d2c4cf842af77e996d0d2854aa2d00b32a0
--- /dev/null
+++ b/ash/desktop_background/desktop_background_widget_controller.cc
@@ -0,0 +1,62 @@
+// 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/desktop_background/desktop_background_widget_controller.h"
+
+#include "ui/aura/root_window.h"
+#include "ui/views/widget/widget.h"
+
+DECLARE_WINDOW_PROPERTY_TYPE(ash::internal::DesktopBackgroundWidgetController*);
+
+namespace ash {
+namespace internal {
+
+DEFINE_OWNED_WINDOW_PROPERTY_KEY(DesktopBackgroundWidgetController,
+                                 kWindowDesktopComponent, NULL);
+
+DesktopBackgroundWidgetController::DesktopBackgroundWidgetController(
+    views::Widget* widget)
+        : widget_(widget) {

[Nikita (slow), 2012/07/28 01:32:17]

nit: lines 19-20 could be combined.

[Denis Kuznetsov (DE-MUC), 2012/07/30 15:40:02]

Done.

+}
+
+DesktopBackgroundWidgetController::DesktopBackgroundWidgetController(
+    ui::Layer* layer)

[Nikita (slow), 2012/07/28 01:32:17]

nit: lines 24-25 could be combined.

[Denis Kuznetsov (DE-MUC), 2012/07/30 15:40:02]

Done.

+        : widget_(NULL) {
+  layer_.reset(layer);
+}
+
+
+DesktopBackgroundWidgetController::~DesktopBackgroundWidgetController() {
+  if (widget_) {
+    widget_->CloseNow();
+    widget_ = NULL;
+  }
+  if (layer_.get())

[Nikita (slow), 2012/07/28 01:32:17]

else if

[Denis Kuznetsov (DE-MUC), 2012/07/30 15:40:02]

Done.

+    layer_.reset(NULL);
+}
+
+void DesktopBackgroundWidgetController::SetBounds(gfx::Rect bounds) {
+  if (widget_)
+    widget_->SetBounds(bounds);
+  if (layer_.get())

[Nikita (slow), 2012/07/28 01:32:17]

else if

[Denis Kuznetsov (DE-MUC), 2012/07/30 15:40:02]

Done.

+    layer_->SetBounds(bounds);
+}
+
+
+void DesktopBackgroundWidgetController::Reparent(aura::RootWindow* root_window,
+                                                 int src_container,
+                                                 int dest_container) {
+  if (widget_) {
+    views::Widget::ReparentNativeView(widget_->GetNativeView(),
+        root_window->GetChildById(dest_container));
+  }
+  if (layer_.get()) {

[Nikita (slow), 2012/07/28 01:32:17]

else if

[Denis Kuznetsov (DE-MUC), 2012/07/30 15:40:02]

Done.

+    ui::Layer* layer = layer_.get();
+    root_window->GetChildById(src_container)->layer()->Remove(layer);
+    root_window->GetChildById(dest_container)->layer()->Add(layer);
+  }
+}
+
+}  // namespace internal
+}  // namespace ash