Set Ash material design mode in tests properly

ash/shelf/shelf_view_unittest.cc

Index: ash/shelf/shelf_view_unittest.cc
diff --git a/ash/shelf/shelf_view_unittest.cc b/ash/shelf/shelf_view_unittest.cc
index 17ebe18112b63585db03eb3f6f094291d69c4443..6d88368b92d430140f2d458adfda437eb078c04a 100644
--- a/ash/shelf/shelf_view_unittest.cc
+++ b/ash/shelf/shelf_view_unittest.cc
@@ -2116,6 +2116,8 @@ class TestAppListShellDelegate : public TestShellDelegate {
 
 }  // namespace
 
+// Test fixture that forces material design mode in order to test ink drop
+// ripples on shelf.
 class ShelfViewInkDropTest : public ShelfViewTest {
  public:
   ShelfViewInkDropTest() {}
@@ -2125,20 +2127,9 @@ class ShelfViewInkDropTest : public ShelfViewTest {
     shell_delegate_ = new TestAppListShellDelegate;
     ash_test_helper()->set_test_shell_delegate(shell_delegate_);
 
-    ShelfViewTest::SetUp();
-
-    // TODO(mohsen): Ideally, we would want to set material mode before calling
-    // ShelfViewTest::SetUp() so that everything is set up with the correct
-    // material mode. Currently, this is not possible as it expects material
-    // mode be UNINITIALIZED. (See https://crbug.com/620093)
-    ash_md_controller_.reset(new ash::test::MaterialDesignControllerTestAPI(
-        ash::MaterialDesignController::MATERIAL_EXPERIMENTAL));
-  }
+    set_material_mode(ash::MaterialDesignController::MATERIAL_EXPERIMENTAL);
 
-  void TearDown() override {
-    ash_md_controller_.reset();
-
-    ShelfViewTest::TearDown();
+    ShelfViewTest::SetUp();
   }
 
  protected:
@@ -2179,9 +2170,6 @@ class ShelfViewInkDropTest : public ShelfViewTest {
     shell_delegate_->app_list_presenter()->FinishVisibilityChange();
   }
 
-  std::unique_ptr<ash::test::MaterialDesignControllerTestAPI>
-      ash_md_controller_;
-
   TestAppListShellDelegate* shell_delegate_ = nullptr;  // Owned by Shell.
 
   AppListButton* app_list_button_ = nullptr;