--- a/mfbt/RefPtr.h
+++ b/mfbt/RefPtr.h
@@ -4,16 +4,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 /* Helpers for defining and using refcounted objects. */
 
 #ifndef mozilla_RefPtr_h
 #define mozilla_RefPtr_h
 
+#include "mozilla/AlreadyAddRefed.h"
 #include "mozilla/Assertions.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/Attributes.h"
 #include "mozilla/RefCountType.h"
 #include "mozilla/TypeTraits.h"
 #if defined(MOZILLA_INTERNAL_API)
 #include "nsXPCOM.h"
 #endif
@@ -230,16 +231,17 @@ class RefPtr
   friend class OutParamRef<T>;
 
   struct DontRef {};
 
 public:
   RefPtr() : mPtr(0) {}
   RefPtr(const RefPtr& aOther) : mPtr(ref(aOther.mPtr)) {}
   MOZ_IMPLICIT RefPtr(const TemporaryRef<T>& aOther) : mPtr(aOther.take()) {}
+  MOZ_IMPLICIT RefPtr(already_AddRefed<T>& aOther) : mPtr(aOther.take()) {}
   MOZ_IMPLICIT RefPtr(T* aVal) : mPtr(ref(aVal)) {}
 
   template<typename U>
   RefPtr(const RefPtr<U>& aOther) : mPtr(ref(aOther.get())) {}
 
   ~RefPtr() { unref(mPtr); }
 
   RefPtr& operator=(const RefPtr& aOther)
@@ -247,16 +249,21 @@ public:
     assign(ref(aOther.mPtr));
     return *this;
   }
   RefPtr& operator=(const TemporaryRef<T>& aOther)
   {
     assign(aOther.take());
     return *this;
   }
+  RefPtr& operator=(const already_AddRefed<T>& aOther)
+  {
+    assign(aOther.take());
+    return *this;
+  }
   RefPtr& operator=(T* aVal)
   {
     assign(ref(aVal));
     return *this;
   }
 
   template<typename U>
   RefPtr& operator=(const RefPtr<U>& aOther)