chromeos: Fix shelf appearing at login screen under mash

ash/common/shelf/shelf_widget.cc

Index: ash/common/shelf/shelf_widget.cc
diff --git a/ash/common/shelf/shelf_widget.cc b/ash/common/shelf/shelf_widget.cc
index 4ebc52eec6e2f401e9dc2457ebc6ad257f9642a1..a288b47823353e9ace2796dfac83f61ddae36e74 100644
--- a/ash/common/shelf/shelf_widget.cc
+++ b/ash/common/shelf/shelf_widget.cc
@@ -331,6 +331,10 @@ void ShelfWidget::PostCreateShelf() {
   // Ensure the newly created |shelf_| gets current values.
   background_animator_.Initialize(this);
 
+  // TODO(jamescook): The IsActiveUserSessionStarted() check may not be needed
+  // because the shelf is only created after the first user session is active.
+  // If the shelf view is always visible after creation then some of the shelf
+  // visibility code could be simplified. http://crbug.com/674773

[msw, 2016/12/16 16:26:20]

What happens for the lock screen? Isn't the shelf hidden then?

[James Cook, 2016/12/20 04:02:42]

Updated comment.

The shelf is hidden at the lock screen because it's in a container that is
hidden.

When auto-hidden it is transparent.

   shelf_view_->SetVisible(
       WmShell::Get()->GetSessionStateDelegate()->IsActiveUserSessionStarted());
   shelf_layout_manager_->LayoutShelf();
@@ -342,11 +346,6 @@ bool ShelfWidget::IsShelfVisible() const {
   return shelf_view_ && shelf_view_->visible();
 }
 
-void ShelfWidget::SetShelfVisibility(bool visible) {
-  if (shelf_view_)
-    shelf_view_->SetVisible(visible);
-}
-
 bool ShelfWidget::IsShowingAppList() const {
   return GetAppListButton() && GetAppListButton()->is_showing_app_list();
 }