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_component.h"
 #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), 2012/07/25 20:45:24]

nit: insert space between // and comment text.

[sky, 2012/07/25 20:47:36]

nit: space after //

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  for (Shell::RootWindowList::iterator iter = root_windows.begin();
+       iter != root_windows.end(); ++iter) {
+    InstallComponent(*iter);
+  }
 }
 
 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;
-  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);
-    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);
-  }
-}
-
-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::UpdateDesktopBackgroundImageMode() {
-  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
-
-  for (Shell::RootWindowList::iterator iter = root_windows.begin();
-       iter != root_windows.end(); ++iter) {
-    SetDesktopBackgroundImage(*iter);
-  }
-  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;
+  SetDesktopBackgroundImageMode();
+}
+
+
+void DesktopBackgroundController::InstallComponent(
+    aura::RootWindow* root_window) {
+  internal::DesktopBackgroundComponent* component = NULL;
+
+  int container_id = locked_ ?
+      internal::kShellWindowId_LockScreenBackgroundContainer :
+      internal::kShellWindowId_DesktopBackgroundContainer;
+
+  switch (desktop_background_mode_) {
+    case BACKGROUND_IMAGE: {
+      views::Widget* widget = internal::CreateDesktopBackground(root_window,
+                                                             container_id);

[Nikita (slow), 2012/07/25 20:45:24]

nit: indentation is off

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+      component = new internal::DesktopBackgroundComponent(widget);
+      break;
+    }
+    case BACKGROUND_SOLID_COLOR: {
+      ui::Layer* layer = SetColorLayerForContainer(background_color_,
+                                                    root_window,

[Nikita (slow), 2012/07/25 20:45:24]

nit: indentation

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+                                                    container_id);
+      component = new internal::DesktopBackgroundComponent(layer);
+      break;
+    }
+  }

[Nikita (slow), 2012/07/25 20:45:24]

default:
  NOTREACHED();

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+  root_window->SetProperty(internal::kWindowDesktopComponent, component);
+}
+
+ui::Layer* DesktopBackgroundController::SetColorLayerForContainer(
+    SkColor color,
+    aura::RootWindow* root_window,
+    int container_id) {
+    ui::Layer* background_layer = new ui::Layer(ui::LAYER_SOLID_COLOR);

[Nikita (slow), 2012/07/25 20:45:24]

Indentation is off.

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+    background_layer->SetColor(color);
+
+    Shell::GetContainer(root_window,container_id)->
+        layer()->Add(background_layer);
+    return background_layer;
+}
+
+void DesktopBackgroundController::SetDesktopBackgroundSolidColorMode(
+    SkColor color) {
+  background_color_ = color;
+  if (desktop_background_mode_ != BACKGROUND_SOLID_COLOR) {
+    desktop_background_mode_ = BACKGROUND_SOLID_COLOR;
+    Shell::RootWindowList root_windows = Shell::GetAllRootWindows();

[Nikita (slow), 2012/07/25 20:45:24]

237-240 could be extracted to a separate function.
261-263

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

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

[Nikita (slow), 2012/07/25 20:45:24]

nit: add {}

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+        InstallComponent(*iter);
+    return;
+  }
+
   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), 2012/07/25 20:45:24]

nit: Fix indent.

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+    aura::RootWindow* root_window = *iter;
+    internal::DesktopBackgroundComponent* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    DCHECK(component->layer());
+    component->layer()->SetColor(background_color_ );
   }
 }
 
+
+void DesktopBackgroundController::SetDesktopBackgroundImageMode() {
+  if (desktop_background_mode_ != BACKGROUND_IMAGE) {
+    desktop_background_mode_ = BACKGROUND_IMAGE;
+    Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+    for (Shell::RootWindowList::iterator iter = root_windows.begin();
+      iter != root_windows.end(); ++iter)

[Nikita (slow), 2012/07/25 20:45:24]

nit: Add {}

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+        InstallComponent(*iter);
+    return;
+  }
+
+  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::DesktopBackgroundComponent* 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()));
+  }
+

[Nikita (slow), 2012/07/25 20:45:24]

nit: nuke empty line

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+}
+
+
+
+void DesktopBackgroundController::CreateLockScreenDesktops() {

[sky, 2012/07/25 20:47:36]

Position should match that of header.

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Done.

+  if (locked_)
+    return;
+  locked_ = true;

[sky, 2012/07/25 20:47:36]

Why do we need locked_ cached in here?

[Denis Kuznetsov (DE-MUC), 2012/07/26 13:51:13]

Because we want to add ui components to correct container, if number of monitors
change while screen is locked (see InstallComponent call from OnRootWindowAdded)

+
+  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::DesktopBackgroundComponent* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    component->Reparent(root_window,
+                        internal::kShellWindowId_DesktopBackgroundContainer,
+                        internal::kShellWindowId_LockScreenBackgroundContainer);
+  }
+}
+
+void DesktopBackgroundController::RemoveLockScreenDesktops() {
+  if (!locked_)
+    return;
+  locked_ = false;
+
+  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::DesktopBackgroundComponent* component = root_window->
+        GetProperty(internal::kWindowDesktopComponent);
+    DCHECK(component);
+    component->Reparent(root_window,
+                        internal::kShellWindowId_LockScreenBackgroundContainer,
+                        internal::kShellWindowId_DesktopBackgroundContainer);
+  }
+}
+
 }  // namespace ash