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

ash/desktop_background/desktop_background_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/desktop_background/desktop_background_controller.h"
 
+#include "ash/desktop_background/desktop_background_widget_controller.h"

[Nikita (slow), 2012/07/28 01:25:25]

nit: sort

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

Done.

 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/shell.h"
 #include "ash/shell_factory.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/root_window_layout_manager.h"
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/synchronization/cancellation_flag.h"
 #include "base/threading/worker_pool.h"
 #include "grit/ui_resources.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/layer.h"
+#include "ui/gfx/rect.h"
 #include "ui/gfx/image/image.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
 namespace {
 internal::RootWindowLayoutManager* GetRootWindowLayoutManager(
     aura::RootWindow* root_window) {
   return static_cast<internal::RootWindowLayoutManager*>(
       root_window->layout_manager());
 }
@@ skipping 53 matching lines @@
   base::CancellationFlag cancel_flag_;
 
   scoped_ptr<WallpaperData> wallpaper_data_;
 
   int index_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperOperation);
 };
 
 DesktopBackgroundController::DesktopBackgroundController()
-    : desktop_background_mode_(BACKGROUND_IMAGE),
+    : locked_(false),
+      desktop_background_mode_(BACKGROUND_SOLID_COLOR),
       background_color_(SK_ColorGRAY),
       weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+  // Install wallpaper component for all available windows.

[Nikita (slow), 2012/07/28 01:25:25]

nit: Not method name speaks for itself, comment should be removed.

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

Done.

+  InstallComponentForAllWindows();
 }
 
 DesktopBackgroundController::~DesktopBackgroundController() {
   CancelPendingWallpaperOperation();
 }
 
 gfx::ImageSkia DesktopBackgroundController::GetWallpaper() const {
   if (current_wallpaper_.get())
     return current_wallpaper_->wallpaper_image;
   return gfx::ImageSkia();
 }
 
 WallpaperLayout DesktopBackgroundController::GetWallpaperLayout() const {
   if (current_wallpaper_.get())
     return current_wallpaper_->wallpaper_layout;
   return CENTER_CROPPED;
 }
 
 SkBitmap DesktopBackgroundController::GetCurrentWallpaperImage() {
   if (desktop_background_mode_ != BACKGROUND_IMAGE)
     return SkBitmap();
   return GetWallpaper();
 }
 
 void DesktopBackgroundController::OnRootWindowAdded(
     aura::RootWindow* root_window) {
-  switch (desktop_background_mode_) {
-    case BACKGROUND_IMAGE:
-      if (current_wallpaper_.get()) {
-        SetDesktopBackgroundImage(root_window);
-      } else {
-        internal::CreateDesktopBackground(root_window);
-      }
-      break;
-    case BACKGROUND_SOLID_COLOR:
-      SetDesktopBackgroundSolidColorMode(background_color_);
-      break;
-  }
+  InstallComponent(root_window);
 }
 
 void DesktopBackgroundController::SetDefaultWallpaper(int index) {
   // We should not change background when index is invalid. For instance, at
   // login screen or stub_user login.
-  if (index == ash::GetInvalidWallpaperIndex()) {
+  if (index == GetInvalidWallpaperIndex()) {
     CreateEmptyWallpaper();
     return;
-  } else if (index == ash::GetSolidColorIndex()) {
+  } else if (index == GetSolidColorIndex()) {
     SetDesktopBackgroundSolidColorMode(kLoginWallpaperColor);
     return;
   }
 
   if (current_wallpaper_.get() && current_wallpaper_->wallpaper_index == index)
     return;
 
   CancelPendingWallpaperOperation();
 
   wallpaper_op_ = new WallpaperOperation(index);
   base::WorkerPool::PostTaskAndReply(
       FROM_HERE,
       base::Bind(&WallpaperOperation::Run, wallpaper_op_),
       base::Bind(&DesktopBackgroundController::OnWallpaperLoadCompleted,
                  weak_ptr_factory_.GetWeakPtr(),
                  wallpaper_op_),
       true /* task_is_slow */);
 }
 
 void DesktopBackgroundController::SetCustomWallpaper(
     const gfx::ImageSkia& wallpaper,
     WallpaperLayout layout) {
   CancelPendingWallpaperOperation();
   current_wallpaper_.reset(new WallpaperData(layout, wallpaper));
-  desktop_background_mode_ = BACKGROUND_IMAGE;
-  UpdateDesktopBackgroundImageMode();
+  SetDesktopBackgroundImageMode();
 }
 
 void DesktopBackgroundController::CancelPendingWallpaperOperation() {
   // Set canceled flag of previous request to skip unneeded loading.
   if (wallpaper_op_.get())
     wallpaper_op_->Cancel();
 
   // Cancel reply callback for previous request.
   weak_ptr_factory_.InvalidateWeakPtrs();
 }
 
 void DesktopBackgroundController::SetDesktopBackgroundSolidColorMode(
     SkColor color) {
-  // Set a solid black background.
-  // TODO(derat): Remove this in favor of having the compositor only clear the
-  // viewport when there are regions not covered by a layer:
-  // http://crbug.com/113445
-  current_wallpaper_.reset(NULL);
   background_color_ = color;
-  desktop_background_mode_ = BACKGROUND_SOLID_COLOR;
+  if (desktop_background_mode_ != BACKGROUND_SOLID_COLOR) {
+    desktop_background_mode_ = BACKGROUND_SOLID_COLOR;
+    InstallComponentForAllWindows();
+    return;
+  }
+
   Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
   for (Shell::RootWindowList::iterator iter = root_windows.begin();
-       iter != root_windows.end(); ++iter) {
-    ui::Layer* background_layer = new ui::Layer(ui::LAYER_SOLID_COLOR);
-    background_layer->SetColor(color);
+      iter != root_windows.end(); ++iter) {

[Nikita (slow), 2012/07/28 01:25:25]

nit: Indentation is not fixed. Should be 

for (Shell::RootWindowList::iterator iter = root_windows.begin();
     iter != root_windows.end(); ++iter) {

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

Done.

     aura::RootWindow* root_window = *iter;
-    Shell::GetContainer(
-        root_window,
-        internal::kShellWindowId_DesktopBackgroundContainer)->
-        layer()->Add(background_layer);
-    GetRootWindowLayoutManager(root_window)->SetBackgroundLayer(
-        background_layer);
-    GetRootWindowLayoutManager(root_window)->SetBackgroundWidget(NULL);
+    internal::DesktopBackgroundWidgetController* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    DCHECK(component->layer());
+    component->layer()->SetColor(background_color_ );
   }
 }
 
-void DesktopBackgroundController::SetDesktopBackgroundImage(
-    aura::RootWindow* root_window) {
-  GetRootWindowLayoutManager(root_window)->SetBackgroundLayer(NULL);
-  if (current_wallpaper_.get() &&
-      !current_wallpaper_->wallpaper_image.empty())
-    internal::CreateDesktopBackground(root_window);
+void DesktopBackgroundController::CreateEmptyWallpaper() {
+  current_wallpaper_.reset(NULL);
+  SetDesktopBackgroundImageMode();
 }
 
-void DesktopBackgroundController::UpdateDesktopBackgroundImageMode() {
+void DesktopBackgroundController::MoveDesktopToLockedContainer() {
+  if (locked_)
+    return;
+  locked_ = true;
+  ReparentBackgroundWidgets(GetBackgroundContainerId(false),
+                            GetBackgroundContainerId(true));
+}
+
+void DesktopBackgroundController::MoveDesktopToUnlockedContainer() {
+  if (!locked_)
+    return;
+  locked_ = false;
+  ReparentBackgroundWidgets(GetBackgroundContainerId(true),
+                            GetBackgroundContainerId(false));
+}
+
+void DesktopBackgroundController::SetDesktopBackgroundImageMode() {
+  if (desktop_background_mode_ != BACKGROUND_IMAGE) {
+    desktop_background_mode_ = BACKGROUND_IMAGE;
+    InstallComponentForAllWindows();
+    return;
+  }
+
   Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
-
   for (Shell::RootWindowList::iterator iter = root_windows.begin();
-       iter != root_windows.end(); ++iter) {
-    SetDesktopBackgroundImage(*iter);
+      iter != root_windows.end(); ++iter) {
+    aura::RootWindow* root_window = *iter;
+    internal::DesktopBackgroundWidgetController* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    DCHECK(component->widget());
+    aura::Window* window = component->widget()->GetNativeView();
+    gfx::Rect bounds = window->bounds();
+    window->SchedulePaintInRect(gfx::Rect(0, 0,
+                                          bounds.width(), bounds.height()));
   }
-  desktop_background_mode_ = BACKGROUND_IMAGE;
 }
 
 void DesktopBackgroundController::OnWallpaperLoadCompleted(
     scoped_refptr<WallpaperOperation> wo) {
   current_wallpaper_.reset(wo->ReleaseWallpaperData());
 
-  UpdateDesktopBackgroundImageMode();
+  SetDesktopBackgroundImageMode();
 
   DCHECK(wo.get() == wallpaper_op_.get());
   wallpaper_op_ = NULL;
 }
 
-void DesktopBackgroundController::CreateEmptyWallpaper() {
-  current_wallpaper_.reset(NULL);
-  desktop_background_mode_ = BACKGROUND_IMAGE;
+ui::Layer* DesktopBackgroundController::SetColorLayerForContainer(
+    SkColor color,
+    aura::RootWindow* root_window,
+    int container_id) {
+  ui::Layer* background_layer = new ui::Layer(ui::LAYER_SOLID_COLOR);
+  background_layer->SetColor(color);
+
+  Shell::GetContainer(root_window,container_id)->
+      layer()->Add(background_layer);
+  return background_layer;
+}
+
+void DesktopBackgroundController::InstallComponent(
+    aura::RootWindow* root_window) {
+  internal::DesktopBackgroundWidgetController* component = NULL;
+  int container_id = GetBackgroundContainerId(locked_);
+
+  switch (desktop_background_mode_) {
+    case BACKGROUND_IMAGE: {
+      views::Widget* widget = internal::CreateDesktopBackground(root_window,
+                                                                container_id);
+      component = new internal::DesktopBackgroundWidgetController(widget);
+      break;
+    }
+    case BACKGROUND_SOLID_COLOR: {
+      ui::Layer* layer = SetColorLayerForContainer(background_color_,
+                                                   root_window,
+                                                   container_id);
+      component = new internal::DesktopBackgroundWidgetController(layer);
+      break;
+    }
+    default:

[Nikita (slow), 2012/07/28 01:25:25]

nit: Should also have {}
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Loops_and_Swit...

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

Done.

+      NOTREACHED();
+  }
+  root_window->SetProperty(internal::kWindowDesktopComponent, component);
+}
+
+void DesktopBackgroundController::InstallComponentForAllWindows() {
   Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
   for (Shell::RootWindowList::iterator iter = root_windows.begin();
-       iter != root_windows.end(); ++iter) {
-    internal::CreateDesktopBackground(*iter);
+      iter != root_windows.end(); ++iter) {

[Nikita (slow), 2012/07/28 01:25:25]

nit: +1 indent space

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

Done.

+    InstallComponent(*iter);
   }
 }
 
+void DesktopBackgroundController::ReparentBackgroundWidgets(int src_container,
+                                                            int dst_container) {
+  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  for (Shell::RootWindowList::iterator iter = root_windows.begin();
+    iter != root_windows.end(); ++iter) {
+    aura::RootWindow* root_window = *iter;
+    internal::DesktopBackgroundWidgetController* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    component->Reparent(root_window,
+                        src_container,
+                        dst_container);
+  }
+}
+
+int DesktopBackgroundController::GetBackgroundContainerId(bool locked) {
+  return  locked ? internal::kShellWindowId_LockScreenBackgroundContainer :

[Nikita (slow), 2012/07/28 01:25:25]

nit: Remove extra space.

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

Done.

+                   internal::kShellWindowId_DesktopBackgroundContainer;
+}
+
 }  // namespace ash