Don't animate the default/background layer if there is no background.

chrome/browser/chromeos/login/base_login_display_host.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 "chrome/browser/chromeos/login/base_login_display_host.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 310 matching lines @@
 #if defined(USE_AURA)
   // Fade out transition for sign in screen.
   // BaseLoginDisplayHost will be deleted this animation is ended.
   ui::Layer* layer = GetLayer(GetWidget());
   layer->GetAnimator()->AddObserver(this);
   ui::LayerAnimator::ScopedSettings signin_animation(layer->GetAnimator());
   signin_animation.SetTransitionDuration(
       base::TimeDelta::FromMilliseconds(kLoginFadeoutTransitionDurationMs));
   layer->SetOpacity(0.0f);
 
+  if (ash::Shell::GetInstance()->GetContainer(
+          ash::internal::kShellWindowId_DesktopBackgroundContainer)->
+          children().empty()) {
+    // If there is no background window, don't perform any animation on the
+    // default and background layer because there is nothing behind it.
+    return;
+  }
+
   // Background animation.
   if (kEnableBackgroundAnimation) {
     ui::Transform background_transform;
     background_transform.SetScale(kBackgroundScale, kBackgroundScale);
     background_transform.SetTranslateX(kBackgroundTranslate);
     background_transform.SetTranslateY(kBackgroundTranslate);
     scoped_ptr<ui::LayerAnimationElement>
         background_transform_animation_initial(
             ui::LayerAnimationElement::CreateTransformElement(
                 background_transform,
@@ skipping 17 matching lines @@
     ui::Layer* background_layer =
         ash::Shell::GetInstance()->GetContainer(
             ash::internal::kShellWindowId_DesktopBackgroundContainer)->
             layer();
     background_layer->GetAnimator()->StartAnimation(
         background_transition.release());
   }
 
   // Browser windows layer opacity animation.
   if (kEnableBrowserWindowsOpacityAnimation) {
-    scoped_ptr<ui::LayerAnimationElement> browser_opacity_animation_initial(
+    scoped_ptr<ui::LayerAnimationElement> br

[Nikita (slow), 2012/01/13 10:16:30]

Please fix.

[oshima, 2012/01/13 18:35:57]

oops. done.

+owser_opacity_animation_initial(
         ui::LayerAnimationElement::CreateOpacityElement(
             0.0f,
             base::TimeDelta()));
     ui::LayerAnimationElement::AnimatableProperties browser_pause_properties;
     browser_pause_properties.insert(ui::LayerAnimationElement::OPACITY);
     scoped_ptr<ui::LayerAnimationElement> browser_pause_animation(
         ui::LayerAnimationElement::CreatePauseElement(
             browser_pause_properties,
             base::TimeDelta::FromMilliseconds(kBrowserTransitionPauseMs)));
     scoped_ptr<ui::LayerAnimationElement> browser_opacity_animation(
@@ skipping 207 matching lines @@
   // user has changed to during OOBE.
   if (!timezone_name.empty()) {
     icu::TimeZone* timezone = icu::TimeZone::createTimeZone(
         icu::UnicodeString::fromUTF8(timezone_name));
     CHECK(timezone) << "Timezone could not be set for " << timezone_name;
     chromeos::system::TimezoneSettings::GetInstance()->SetTimezone(*timezone);
   }
 }
 
 }  // namespace browser