Set Ash material design mode in tests properly

ash/test/ash_md_test_base.cc

Index: ash/test/ash_md_test_base.cc
diff --git a/ash/test/ash_md_test_base.cc b/ash/test/ash_md_test_base.cc
index fee38416a353192c4c4ee6c2f27f1195bdff4b12..7e7418e5a1d60facf9182b5af9d3edf93daca565 100644
--- a/ash/test/ash_md_test_base.cc
+++ b/ash/test/ash_md_test_base.cc
@@ -15,28 +15,31 @@ AshMDTestBase::AshMDTestBase() {}
 AshMDTestBase::~AshMDTestBase() {}
 
 void AshMDTestBase::SetUp() {
-  AshTestBase::SetUp();
-
-  material_design_state_.reset(new test::MaterialDesignControllerTestAPI(
-      MaterialDesignController::Mode::NON_MATERIAL));
-  const int non_md_shelf_size = GetShelfConstant(SHELF_SIZE);
-  const int non_md_auto_hide_shelf_size =
-      GetShelfConstant(SHELF_INSETS_FOR_AUTO_HIDE);
-
-  material_design_state_.reset(
-      new test::MaterialDesignControllerTestAPI(GetParam()));
-  const int md_state_shelf_size = GetShelfConstant(SHELF_SIZE);
-  const int md_state_auto_hide_shelf_size =
-      GetShelfConstant(SHELF_INSETS_FOR_AUTO_HIDE);
-
-  md_maximized_window_height_offset_ = non_md_shelf_size - md_state_shelf_size;
+  int non_md_shelf_size = 0;
+  int non_md_auto_hide_shelf_size = 0;
+  int md_shelf_size = 0;
+  int md_auto_hide_shelf_size = 0;
+
+  {
+    test::MaterialDesignControllerTestAPI md_state(
+        MaterialDesignController::Mode::NON_MATERIAL);
+    non_md_shelf_size = GetShelfConstant(SHELF_SIZE);
+    non_md_auto_hide_shelf_size = GetShelfConstant(SHELF_INSETS_FOR_AUTO_HIDE);
+  }
+
+  {
+    test::MaterialDesignControllerTestAPI md_state(GetParam());
+    md_shelf_size = GetShelfConstant(SHELF_SIZE);
+    md_auto_hide_shelf_size = GetShelfConstant(SHELF_INSETS_FOR_AUTO_HIDE);
+  }
+
+  md_maximized_window_height_offset_ = non_md_shelf_size - md_shelf_size;
   md_auto_hidden_shelf_height_offset_ =
-      non_md_auto_hide_shelf_size - md_state_auto_hide_shelf_size;
-}
+      non_md_auto_hide_shelf_size - md_auto_hide_shelf_size;
+
+  set_material_mode(GetParam());
 
-void AshMDTestBase::TearDown() {
-  material_design_state_.reset();
-  AshTestBase::TearDown();
+  AshTestBase::SetUp();
 }
 
 int AshMDTestBase::GetMdMaximizedWindowHeightOffset() {