Separate ash::test::DisplayManagerTestApi from ash

ash/wm/workspace/workspace_layout_manager_unittest.cc

Index: ash/wm/workspace/workspace_layout_manager_unittest.cc
diff --git a/ash/wm/workspace/workspace_layout_manager_unittest.cc b/ash/wm/workspace/workspace_layout_manager_unittest.cc
index bc492d9ee7adf1ab0943348978e3e0ef9bb2c2c8..0332c25edebce9004c34973ae22bd9f51ad2a9e1 100644
--- a/ash/wm/workspace/workspace_layout_manager_unittest.cc
+++ b/ash/wm/workspace/workspace_layout_manager_unittest.cc
@@ -121,7 +121,7 @@ TEST_F(WorkspaceLayoutManagerTest, RestoreFromMinimizeKeepsRestore) {
 
   UpdateDisplay("400x300,500x400");
   window->SetBoundsInScreen(gfx::Rect(600, 0, 100, 100),
-                            ScreenUtil::GetSecondaryDisplay());
+                            display_manager()->GetSecondaryDisplay());
   EXPECT_EQ(Shell::GetAllRootWindows()[1], window->GetRootWindow());
   window_state->Minimize();
   // This will not be used for un-minimizing window.
@@ -147,7 +147,8 @@ TEST_F(WorkspaceLayoutManagerTest, KeepMinimumVisibilityInDisplays) {
   aura::Window::Windows root_windows = Shell::GetAllRootWindows();
 
   Shell::GetInstance()->display_manager()->SetLayoutForCurrentDisplays(
-      test::CreateDisplayLayout(display::DisplayPlacement::TOP, 0));
+      test::CreateDisplayLayout(display_manager(),
+                                display::DisplayPlacement::TOP, 0));
   EXPECT_EQ("0,-500 400x500", root_windows[1]->GetBoundsInScreen().ToString());
 
   std::unique_ptr<aura::Window> window1(