Separate ash::test::DisplayManagerTestApi from ash

ash/display/unified_mouse_warp_controller.h

Index: ash/display/unified_mouse_warp_controller.h
diff --git a/ash/display/unified_mouse_warp_controller.h b/ash/display/unified_mouse_warp_controller.h
index 639d146fb3e7d5a00bf68ed17d8f677f44e70e23..e257bc871e618728a17026f8b33e6e24bff3e668 100644
--- a/ash/display/unified_mouse_warp_controller.h
+++ b/ash/display/unified_mouse_warp_controller.h
@@ -22,6 +22,7 @@ class Point;
 
 namespace ash {
 namespace test {
+class AshTestBase;
 class DisplayManagerTestApi;
 }
 
@@ -36,6 +37,7 @@ class ASH_EXPORT UnifiedMouseWarpController : public MouseWarpController {
   void SetEnabled(bool enabled) override;
 
  private:
+  friend class test::AshTestBase;
   friend class test::DisplayManagerTestApi;
   friend class UnifiedMouseWarpControllerTest;