Draggable peeking/fullscreen launcher with transparent background.

ash/app_list/app_list_presenter_delegate.cc

Index: ash/app_list/app_list_presenter_delegate.cc
diff --git a/ash/app_list/app_list_presenter_delegate.cc b/ash/app_list/app_list_presenter_delegate.cc
index 258a88d4903e4a7b8a6073e9559ac0ccb668cbca..8d4f4c94bcae4c71666cade7b14786845b9b4869 100644
--- a/ash/app_list/app_list_presenter_delegate.cc
+++ b/ash/app_list/app_list_presenter_delegate.cc
@@ -129,6 +129,14 @@ void AppListPresenterDelegate::OnShown(int64_t display_id) {
       Shelf::ForWindow(root_window)->shelf_widget()->GetAppListButton();
   if (app_list_button)
     app_list_button->OnAppListShown();
+
+  // Notify the shelf that the app list is active so the backgrounds do not
+  // overlap.
+
+  if (app_list::features::IsFullscreenAppListEnabled()) {
+    Shelf* shelf = Shelf::ForWindow(root_window);
+    shelf->OnAppListIsActive(true);
+  }
 }
 
 void AppListPresenterDelegate::OnDismissed() {
@@ -142,6 +150,11 @@ void AppListPresenterDelegate::OnDismissed() {
   AppListButton* app_list_button = shelf->shelf_widget()->GetAppListButton();
   if (app_list_button)
     app_list_button->OnAppListDismissed();
+  if (app_list::features::IsFullscreenAppListEnabled()) {
+    // Notify the shelf that the app list is being dismissed so it can
+    // re-enable its transparent background.
+    shelf->OnAppListIsActive(false);
+  }
 }
 
 void AppListPresenterDelegate::UpdateBounds() {