base: Add RetainedRef for unwrapping scoped_refptrs.

base/bind_helpers.h

Index: base/bind_helpers.h
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index 117fc68e177d59afe3c7dba93b2cd77ebb006a03..735c1aa726f1ae749760d8f039b785d5b2ddc7e9 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -312,6 +312,16 @@ class ConstRefWrapper {
 };
 
 template <typename T>
+class RetainedRefWrapper {
+ public:
+  explicit RetainedRefWrapper(T* o) : ptr_(o) {}
+  explicit RetainedRefWrapper(scoped_refptr<T> o) : ptr_(std::move(o)) {}
+  T* get() const { return ptr_.get(); }
+ private:
+  scoped_refptr<T> ptr_;
+};
+
+template <typename T>
 struct IgnoreResultHelper {
   explicit IgnoreResultHelper(T functor) : functor_(functor) {}
 
@@ -410,6 +420,11 @@ T* Unwrap(const scoped_refptr<T>& o) {
 }
 
 template <typename T>
+T* Unwrap(const RetainedRefWrapper<T>& o) {
+  return o.get();
+}
+
+template <typename T>
 const WeakPtr<T>& Unwrap(const WeakPtr<T>& o) {
   return o;
 }
@@ -545,6 +560,16 @@ static inline internal::UnretainedWrapper<T> Unretained(T* o) {
 }
 
 template <typename T>
+static inline internal::RetainedRefWrapper<T> RetainedRef(T* o) {
+  return internal::RetainedRefWrapper<T>(o);
+}
+
+template <typename T>
+static inline internal::RetainedRefWrapper<T> RetainedRef(scoped_refptr<T> o) {
+  return internal::RetainedRefWrapper<T>(std::move(o));
+}
+
+template <typename T>
 static inline internal::ConstRefWrapper<T> ConstRef(const T& o) {
   return internal::ConstRefWrapper<T>(o);
 }