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..fcb6d9503d42bab989dea92975173e493c95ea10 100644
--- a/ash/app_list/app_list_presenter_delegate.cc
+++ b/ash/app_list/app_list_presenter_delegate.cc
@@ -129,6 +129,13 @@ void AppListPresenterDelegate::OnShown(int64_t display_id) {
       Shelf::ForWindow(root_window)->shelf_widget()->GetAppListButton();

[sky, 2017/05/31 15:04:17]

I prefer minimizing direct dependencies between classes and using observers. How
about adding ShellObserver::OnAppListShown()? This code would call to Shell to
notify observers and shelf could observe said function. Shelf would use this
function to both update the applistbutton (as done on 131) as well as the new
functionality you are adding.

[newcomer, 2017/06/01 01:42:54]

Done.

   if (app_list_button)
     app_list_button->OnAppListShown();
+
+  if (app_list::features::IsFullscreenAppListEnabled()) {
+    // Notify the shelf that the app list is active so the backgrounds do not
+    // overlap.
+    Shelf* shelf = Shelf::ForWindow(root_window);
+    shelf->OnAppListIsActive(true);

[xiyuan, 2017/05/30 22:18:50]

nit: Get rid of |shelf| and use Shelf::ForWindow in-place.

[newcomer, 2017/06/01 01:42:53]

Done.

+  }
 }
 
 void AppListPresenterDelegate::OnDismissed() {
@@ -142,6 +149,11 @@ 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() {