Add fade to white animation when power button is pressed on Athena

athena/screen/screen_animator_impl.cc

Index: athena/screen/screen_animator_impl.cc
diff --git a/athena/screen/screen_animator_impl.cc b/athena/screen/screen_animator_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1e9666550628fd4baa6fa870451ad4c44e7b8edd
--- /dev/null
+++ b/athena/screen/screen_animator_impl.cc
@@ -0,0 +1,74 @@
+// Copyright 2014 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 "athena/screen/screen_animator_impl.h"
+
+#include "ui/aura/window.h"
+#include "ui/compositor/layer.h"
+#include "ui/compositor/layer_animation_observer.h"
+#include "ui/compositor/scoped_layer_animation_settings.h"
+#include "ui/gfx/animation/tween.h"
+
+namespace athena {
+namespace {
+
+// Duration of the shutdown animation.
+const int kShutdownDurationMs = 1000;
+
+// Duration of the cancel shutdown animation.
+const int kCancelShutdownDurationMs = 500;
+
+// Animates |window|'s grayscale and brightness to |target|. If non-NULL,
+// |observer| will be notified when the animation completes.
+void StartGrayscaleAndBrightnessAnimation(
+    aura::Window* window,
+    float target,
+    int duration_ms,
+    gfx::Tween::Type tween_type,
+    ui::ImplicitAnimationObserver* observer) {
+  ui::Layer* layer = window->layer();
+  ui::ScopedLayerAnimationSettings settings(layer->GetAnimator());
+  settings.SetTransitionDuration(
+      base::TimeDelta::FromMilliseconds(duration_ms));
+  settings.SetTweenType(tween_type);
+  settings.SetPreemptionStrategy(
+      ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
+  if (observer)
+    settings.AddObserver(observer);
+
+  layer->SetLayerBrightness(target);
+  layer->SetLayerGrayscale(target);
+}
+
+}  // namespace
+
+ScreenAnimatorImpl::ScreenAnimatorImpl(aura::Window* root_window)
+    : root_window_(root_window) {
+}
+
+ScreenAnimatorImpl::~ScreenAnimatorImpl() {
+}
+
+void ScreenAnimatorImpl::StartAnimation(
+    AnimationType type,
+    ui::ImplicitAnimationObserver* observer) {
+  switch (type) {
+    case ANIMATION_SHUTDOWN:
+      StartGrayscaleAndBrightnessAnimation(root_window_,
+                                           1.0f,
+                                           kShutdownDurationMs,
+                                           gfx::Tween::EASE_IN,
+                                           observer);
+      break;
+    case ANIMATION_CANCEL_SHUTDOWN:
+      StartGrayscaleAndBrightnessAnimation(root_window_,
+                                           0.0f,
+                                           kCancelShutdownDurationMs,
+                                           gfx::Tween::EASE_IN_OUT,
+                                           observer);
+      break;
+  }
+}
+
+}  // namespace athena