base::EmplaceUnique

ui/views/controls/scroll_view_unittest.cc

Index: ui/views/controls/scroll_view_unittest.cc
diff --git a/ui/views/controls/scroll_view_unittest.cc b/ui/views/controls/scroll_view_unittest.cc
index 9a9b002ff84e39b2c01d718c9a8c14c90ba13f7b..6b119f547fe0b9c37bbebc94df6f42fecc53308a 100644
--- a/ui/views/controls/scroll_view_unittest.cc
+++ b/ui/views/controls/scroll_view_unittest.cc
@@ -8,6 +8,7 @@
 #include "base/run_loop.h"
 #include "base/test/test_timeouts.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "base/tuple.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/scrollbar/base_scroll_bar_thumb.h"
@@ -21,6 +22,40 @@
 #include "ui/base/test/scoped_preferred_scroller_style_mac.h"
 #endif
 
+namespace base {
+namespace internal {
+
+template <typename... Args>
+struct EmplaceUniqueResult {
+  using Tuple = std::tuple<Args...>;
+  Tuple params;
+
+  EmplaceUniqueResult(Args&&... args)
+      : params(std::forward<Args...>(args...)) {}
+
+  template <class T, std::size_t... I>
+  T* CreateNewT(IndexSequence<I...>) {
+    return new T(std::get<I>(params)...);
+  }
+
+  template <class T>
+  using UniquePtr = std::unique_ptr<T>;  // Avoids a presumbmit error.
+
+  template <class T>
+  operator UniquePtr<T>() {
+    return UniquePtr<T>(CreateNewT<T>(MakeIndexSequenceForTuple<Tuple>()));
+  }
+};
+
+}  // namespace internal
+
+template <typename... Args>
+typename internal::EmplaceUniqueResult<Args...> EmplaceUnique(Args&&... args) {
+  return internal::EmplaceUniqueResult<Args...>(std::forward<Args...>(args...));
+}
+
+}  // namespace base
+
 enum ScrollBarOrientation { HORIZONTAL, VERTICAL };
 
 namespace views {
@@ -151,8 +186,7 @@ class ScrollViewTest : public testing::Test {
     // Ensure the old scroller override is destroyed before creating a new one.
     // Otherwise, the swizzlers are interleaved and restore incorrect methods.
     scroller_style_.reset();
-    scroller_style_ =
-        base::MakeUnique<ui::test::ScopedPreferredScrollerStyle>(enabled);
+    scroller_style_ = base::EmplaceUnique(enabled);
   }
 
  private: