Readd base::UnwrapTraits to support rvalue-reference wrappers

base/bind_helpers_unittest.cc

Index: base/bind_helpers_unittest.cc
diff --git a/base/bind_helpers_unittest.cc b/base/bind_helpers_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9d56b971b53ea2aabbcbd1a2532d9691482dd74f
--- /dev/null
+++ b/base/bind_helpers_unittest.cc
@@ -0,0 +1,50 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/bind_helpers.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/memory/ref_counted.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace base {
+
+TEST(BindHelpersTest, UnwrapUnretained) {
+  int i = 0;
+  auto unretained = Unretained(&i);
+  EXPECT_EQ(&i, internal::Unwrap(unretained));
+  EXPECT_EQ(&i, internal::Unwrap(std::move(unretained)));
+}
+
+TEST(BindHelpersTest, UnwrapConstRef) {
+  int p = 0;
+  auto const_ref = ConstRef(p);
+  EXPECT_EQ(&p, &internal::Unwrap(const_ref));
+  EXPECT_EQ(&p, &internal::Unwrap(std::move(const_ref)));
+}
+
+TEST(BindHelpersTest, UnwrapRetainedRef) {
+  auto p = make_scoped_refptr(new RefCountedData<int>);
+  auto retained_ref = RetainedRef(p);
+  EXPECT_EQ(p.get(), internal::Unwrap(retained_ref));
+  EXPECT_EQ(p.get(), internal::Unwrap(std::move(retained_ref)));
+}
+
+TEST(BindHelpersTest, UnwrapOwned) {
+  int* p = new int;
+  auto owned = Owned(p);
+  EXPECT_EQ(p, internal::Unwrap(owned));
+  EXPECT_EQ(p, internal::Unwrap(std::move(owned)));
+}
+
+TEST(BindHelpersTest, UnwrapPassed) {
+  int* p = new int;
+  auto passed = Passed(WrapUnique(p));
+  EXPECT_EQ(p, internal::Unwrap(passed).get());
+
+  p = new int;
+  EXPECT_EQ(p, internal::Unwrap(Passed(WrapUnique(p))).get());
+}
+
+}  // namespace base