Separate ash::test::DisplayManagerTestApi from ash

ash/wm/dock/docked_window_layout_manager_unittest.cc

Index: ash/wm/dock/docked_window_layout_manager_unittest.cc
diff --git a/ash/wm/dock/docked_window_layout_manager_unittest.cc b/ash/wm/dock/docked_window_layout_manager_unittest.cc
index 71797734338860099f58827ecb475c7f9cf4acc7..00efb45ee7ba30d78b6887e90a88739927a648df 100644
--- a/ash/wm/dock/docked_window_layout_manager_unittest.cc
+++ b/ash/wm/dock/docked_window_layout_manager_unittest.cc
@@ -516,7 +516,8 @@ TEST_P(DockedWindowLayoutManagerTest, ThreeWindowsDraggingSecondScreen) {
   // Layout the secondary display to the bottom of the primary.
   ASSERT_GT(display::Screen::GetScreen()->GetNumDisplays(), 1);
   Shell::GetInstance()->display_manager()->SetLayoutForCurrentDisplays(
-      test::CreateDisplayLayout(display::DisplayPlacement::BOTTOM, 0));
+      test::CreateDisplayLayout(display_manager(),
+                                display::DisplayPlacement::BOTTOM, 0));
 
   std::unique_ptr<aura::Window> w1(
       CreateTestWindow(gfx::Rect(0, 1000, 201, 310)));