Set Ash material design mode in tests properly

ash/test/ash_md_test_base.h

Index: ash/test/ash_md_test_base.h
diff --git a/ash/test/ash_md_test_base.h b/ash/test/ash_md_test_base.h
index 922071be712b0ce9f9a2ea25313e3ab5769d00b0..1d713458706c64bf3c7d85d4c8991178cd2b1b00 100644
--- a/ash/test/ash_md_test_base.h
+++ b/ash/test/ash_md_test_base.h
@@ -21,14 +21,11 @@ class AshMDTestBase
 
   // AshTestBase:
   void SetUp() override;
-  void TearDown() override;
 
   int GetMdMaximizedWindowHeightOffset();
   int GetMdAutoHiddenShelfHeightOffset();
 
  private:
-  std::unique_ptr<MaterialDesignControllerTestAPI> material_design_state_;
-
   // The material design shelf is taller (by 1px) so use this offset to
   // adjust the expected height of a maximized window.
   int md_maximized_window_height_offset_ = 0;