Bug 656059 - Add operator-> to mozilla::DebugOnly<T> so it can store pointers. r=cjones

--HG--
extra : rebase_source : 3d7aeec93f1ae1e5bbd4b03c30216e70fe15eb6a

mfbt/Util.h

@@ -113,6 +113,8 @@ struct DebugOnly
     operator T&() { return value; }
     operator const T&() const { return value; }
 
+    T& operator->() { return value; }
+
 #else
     DebugOnly() {}
     DebugOnly(const T&) {}