Support scoped_refptr<> as the object for a method call in base::Bind(). Reduce useless copies.

base/bind_helpers.h

Index: base/bind_helpers.h
diff --git a/base/bind_helpers.h b/base/bind_helpers.h
index 7eb5716caef4f7b566f0026ad57f91d7a373ace7..07f11f98d2cde4e730b0c811e6b176dac1fa9ca7 100644
--- a/base/bind_helpers.h
+++ b/base/bind_helpers.h
@@ -227,6 +227,11 @@ const T& Unwrap(ConstRefWrapper<T> const_ref) {
   return const_ref.get();
 }
 
+template <typename T>
+T* Unwrap(const scoped_refptr<T>& o) { return o.get(); }
+
+template <typename T>
+const WeakPtr<T>& Unwrap(const WeakPtr<T>& o) { return o; }
 
 // Utility for handling different refcounting semantics in the Bind()
 // function.
@@ -257,6 +262,14 @@ struct MaybeRefcount<base::true_type, T*> {
   static void Release(T* o) { o->Release(); }
 };
 
+// No need to additionally AddRef() and Release() since we are storing a
+// scoped_refptr<> inside the storage object already.
+template <typename T>
+struct MaybeRefcount<base::true_type, scoped_refptr<T> > {
+  static void AddRef(const scoped_refptr<T>& o) {}
+  static void Release(const scoped_refptr<T>& o) {}
+};
+
 template <typename T>
 struct MaybeRefcount<base::true_type, const T*> {
   static void AddRef(const T* o) { o->AddRef(); }