Implement animation UI for opening/closing an app list folder.

ui/app_list/views/apps_grid_view.cc

Index: ui/app_list/views/apps_grid_view.cc
diff --git a/ui/app_list/views/apps_grid_view.cc b/ui/app_list/views/apps_grid_view.cc
index 096ea70802192126420f1f25ceebe14cda7b2707..768c4aae45b21876444bf26470937004e680fd07 100644
--- a/ui/app_list/views/apps_grid_view.cc
+++ b/ui/app_list/views/apps_grid_view.cc
@@ -16,6 +16,7 @@
 #include "ui/app_list/app_list_switches.h"
 #include "ui/app_list/pagination_model.h"
 #include "ui/app_list/views/app_list_drag_and_drop_host.h"
+#include "ui/app_list/views/app_list_folder_view.h"
 #include "ui/app_list/views/app_list_item_view.h"
 #include "ui/app_list/views/apps_grid_view_delegate.h"
 #include "ui/app_list/views/page_switcher.h"
@@ -347,7 +348,12 @@ AppsGridView::AppsGridView(AppsGridViewDelegate* delegate,
       page_flip_target_(-1),
       page_flip_delay_in_ms_(kPageFlipDelayInMs),
       bounds_animator_(this),
-      is_root_level_(true) {
+      is_root_level_(true),
+      activated_item_view_(NULL),
+      animate_to_show_(false) {
+  SetPaintToLayer(true);
+  SetFillsBoundsOpaquely(false);
+
   pagination_model_->AddObserver(this);
   AddChildView(page_switcher_view_);
 
@@ -658,6 +664,37 @@ void AppsGridView::StopPageFlipTimer() {
   page_flip_target_ = -1;
 }
 
+AppListItemView* AppsGridView::GetItemViewAt(int index) const {
+  DCHECK(index >= 0 && index < view_model_.view_size());
+  return static_cast<AppListItemView*>(view_model_.view_at(index));
+}
+
+void AppsGridView::ShowTopItemViews(bool show) {
+  int top_item_count = std::min(static_cast<int>(kNumFolderTopItems),
+                                view_model_.view_size());
+  for (int i = 0; i < top_item_count; ++i)
+    GetItemViewAt(i)->SetVisible(show);
+}
+
+void AppsGridView::ScheduleAnimationToShow(bool show) {
+  // Stop any previous animation.
+  layer()->GetAnimator()->StopAnimating();
+
+  animate_to_show_ = show;
+
+  // Set initial state.
+  SetVisible(true);
+  layer()->SetOpacity(show ? 0.0f : 1.0f);
+
+  ui::ScopedLayerAnimationSettings animation(layer()->GetAnimator());
+  animation.AddObserver(this);
+  animation.SetTweenType(gfx::Tween::EASE_IN_2);
+  animation.SetTransitionDuration(base::TimeDelta::FromMilliseconds(
+      show ? kFolderTransitionInDurationMs : kFolderTransitionOutDurationMs));
+
+  layer()->SetOpacity(show ? 1.0f : 0.0f);
+}
+
 bool AppsGridView::IsDraggedView(const views::View* view) const {
   return drag_view_ == view;
 }
@@ -1401,6 +1438,7 @@ void AppsGridView::ButtonPressed(views::Button* sender,
     return;
 
   if (delegate_) {
+    activated_item_view_ = static_cast<AppListItemView*>(sender);
     delegate_->ActivateApp(static_cast<AppListItemView*>(sender)->item(),
                            event.flags());
   }
@@ -1508,6 +1546,11 @@ void AppsGridView::SetViewHidden(views::View* view, bool hide, bool immediate) {
 #endif
 }
 
+void AppsGridView::OnImplicitAnimationsCompleted() {
+  if (!animate_to_show_)
+    SetVisible(false);
+}
+
 bool AppsGridView::EnableFolderDragDropUI() {
   // Enable drag and drop folder UI only if it is at the app list root level
   // and the switch is on and the target folder can still accept new items.