chromeos: Fix shelf appearing at login screen under mash

ash/common/shelf/shelf_widget.cc

 // Copyright 2012 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 "ash/common/shelf/shelf_widget.h"
 
 #include "ash/common/focus_cycler.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shelf/app_list_button.h"
@@ skipping 313 matching lines @@
   GetContentsView()->AddChildView(shelf_view_);
   return shelf_view_;
 }
 
 void ShelfWidget::PostCreateShelf() {
   SetFocusCycler(WmShell::Get()->focus_cycler());
 
   // 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();
   shelf_layout_manager_->UpdateAutoHideState();
   Show();
 }
 
 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();
 }
 
 bool ShelfWidget::IsShowingContextMenu() const {
   return shelf_view_ && shelf_view_->IsShowingMenu();
 }
 
 bool ShelfWidget::IsShowingOverflowBubble() const {
   return shelf_view_ && shelf_view_->IsShowingOverflowBubble();
@@ skipping 67 matching lines @@
   if (shelf_view_)
     shelf_view_->UpdateShelfItemBackground(alpha);
 }
 
 void ShelfWidget::WillDeleteShelfLayoutManager() {
   shelf_layout_manager_->RemoveObserver(this);
   shelf_layout_manager_ = nullptr;
 }
 
 }  // namespace ash