Save and restore unified mode

ash/display/display_manager_unittest.cc

Index: ash/display/display_manager_unittest.cc
diff --git a/ash/display/display_manager_unittest.cc b/ash/display/display_manager_unittest.cc
index d9dda9e760a343652cdca99f1d93c633ceecd1a5..3e9809d166bd1c4d9eda0e4855d94319f9f2bc5b 100644
--- a/ash/display/display_manager_unittest.cc
+++ b/ash/display/display_manager_unittest.cc
@@ -1463,6 +1463,8 @@ TEST_F(DisplayManagerTest, MAYBE_UpdateDisplayWithHostOrigin) {
 TEST_F(DisplayManagerTest, UnifiedDesktopBasic) {
   if (!SupportsMultipleDisplays())
     return;
+  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
@@ -1500,6 +1502,8 @@ TEST_F(DisplayManagerTest, UnifiedDesktopBasic) {
 TEST_F(DisplayManagerTest, RotateUnifiedDesktop) {
   if (!SupportsMultipleDisplays())
     return;
+  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);
 
@@ -1527,6 +1531,8 @@ TEST_F(DisplayManagerTest, RotateUnifiedDesktop) {
 TEST_F(DisplayManagerTest, UnifiedWithDockWindows) {
   if (!SupportsMultipleDisplays())
     return;
+  test::DisplayManagerTestApi::EnableUnifiedDesktopForTest();
+
   // Don't check root window destruction in unified mode.
   Shell::GetPrimaryRootWindow()->RemoveObserver(this);