Added 1 liner to fix shelf background hiding on side shelf alignment.

ash/app_list/app_list_presenter_delegate_unittest.cc

Index: ash/app_list/app_list_presenter_delegate_unittest.cc
diff --git a/ash/app_list/app_list_presenter_delegate_unittest.cc b/ash/app_list/app_list_presenter_delegate_unittest.cc
index 42eaa1309f31e61eaa4f1b3f6c3277d04d1b6c8e..948fb78a34b369d9443e4b2f166ac6fa707a1c81 100644
--- a/ash/app_list/app_list_presenter_delegate_unittest.cc
+++ b/ash/app_list/app_list_presenter_delegate_unittest.cc
@@ -6,7 +6,10 @@
 
 #include "ash/ash_switches.h"
 #include "ash/public/cpp/config.h"
+#include "ash/public/cpp/shelf_types.h"
 #include "ash/public/cpp/shell_window_ids.h"
+#include "ash/shelf/shelf.h"
+#include "ash/shelf/shelf_layout_manager.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "ash/test/test_app_list_view_presenter_impl.h"
@@ -230,4 +233,33 @@ TEST_F(AppListPresenterDelegateTest, TapAndClickOutsideClosesPeekingAppList) {
   EXPECT_FALSE(app_list_presenter_impl()->GetTargetVisibility());
 }
 
+// Tests that the shelf background displays/hides with bottom shelf
+// alignment.
+TEST_F(AppListPresenterDelegateTest,
+       ShelfBackgroundRespondsToAppListBeingShown) {
+  // TODO(newcomer): Investigate mash failures crbug.com/726838
+   if (Shell::GetAshConfig() == Config::MASH)
+     return;
+  EnableFullscreenAppList();
+  GetPrimaryShelf()->SetAlignment(SHELF_ALIGNMENT_BOTTOM);
+
+  // Show the app list, the shelf background should be transparent.
+  app_list_presenter_impl()->Show(GetPrimaryDisplayId());
+  ShelfLayoutManager* shelf_layout_manager =
+      GetPrimaryShelf()->shelf_layout_manager();
+  EXPECT_EQ(shelf_layout_manager->GetShelfBackgroundType(),
+            SHELF_BACKGROUND_DEFAULT);
+  app_list_presenter_impl()->Dismiss();
+
+  // Set the alignment to the side and show the app list. The background should
+  // show.
+  GetPrimaryShelf()->SetAlignment(ShelfAlignment::SHELF_ALIGNMENT_LEFT);
+  app_list_presenter_impl()->Show(GetPrimaryDisplayId());
+  EXPECT_TRUE(app_list::features::IsFullscreenAppListEnabled());
+  EXPECT_FALSE(GetPrimaryShelf()->IsHorizontalAlignment());
+  EXPECT_EQ(GetPrimaryShelf()->shelf_layout_manager()->
+            GetShelfBackgroundType(),
+            SHELF_BACKGROUND_DEFAULT);
+}
+
 }  // namespace ash