Hide docked windows behind a flag

ash/display/display_manager_unittest.cc

 // Copyright (c) 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 "ui/display/manager/display_manager.h"
 
 #include "ash/accelerators/accelerator_commands_aura.h"
+#include "ash/common/ash_switches.h"
 #include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/wm/window_state.h"
 #include "ash/display/display_configuration_controller.h"
 #include "ash/display/display_util.h"
 #include "ash/display/mirror_window_controller.h"
 #include "ash/display/window_tree_host_manager.h"
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/test/ash_md_test_base.h"
 #include "ash/test/ash_test_base.h"
@@ skipping 2247 matching lines @@
 
   UpdateDisplay("400x500");
   EXPECT_EQ("400x500", screen->GetPrimaryDisplay().size().ToString());
 }
 
 // Makes sure the transition from unified to single won't crash
 // with docked windows.
 TEST_P(DisplayManagerTest, UnifiedWithDockWindows) {
   if (!SupportsMultipleDisplays())
     return;
+
+  // Enable window docking for this test.
+  base::CommandLine::ForCurrentProcess()->AppendSwitch(
+      ash::switches::kAshEnableDockedWindows);
+
   const int height_offset = GetMdMaximizedWindowHeightOffset();
   display_manager()->SetUnifiedDesktopEnabled(true);
 
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
   UpdateDisplay("400x500,300x200");
 
   std::unique_ptr<aura::Window> docked(
       CreateTestWindowInShellWithBounds(gfx::Rect(10, 10, 50, 50)));
@@ skipping 272 matching lines @@
   const display::DisplayLayout& stored =
       layout_store->GetRegisteredDisplayLayout(list);
 
   EXPECT_EQ(id1, stored.placement_list[0].parent_display_id);
   EXPECT_EQ(id2, stored.placement_list[0].display_id);
 }
 
 #endif  // OS_CHROMEOS
 
 }  // namespace ash