Bug 1743020 - Part 4: Use MoveOnlyFunction in DataPipe, r=ipc-reviewers,mccr8

This is mostly a simple use-case for the type which I was aware of and
could use to ensure it builds correctly.

Differential Revision: https://phabricator.services.mozilla.com/D145692

ipc/glue/DataPipe.cpp

@@ -10,6 +10,7 @@
 #include "mozilla/CheckedInt.h"
 #include "mozilla/ErrorNames.h"
 #include "mozilla/Logging.h"
+#include "mozilla/MoveOnlyFunction.h"
 #include "mozilla/ipc/InputStreamParams.h"
 #include "nsIAsyncInputStream.h"
 #include "nsStreamUtils.h"
@@ -35,33 +36,19 @@ class SCOPED_CAPABILITY DataPipeAutoLock {
 
   template <typename F>
   void AddUnlockAction(F aAction) {
-    mActions.AppendElement(MakeUnique<Action<F>>(std::move(aAction)));
+    mActions.AppendElement(std::move(aAction));
   }
 
   ~DataPipeAutoLock() CAPABILITY_RELEASE() {
     mMutex.Unlock();
     for (auto& action : mActions) {
-      action->Run();
+      action();
     }
   }
 
  private:
-  // NOTE: This would be better served by something like llvm's
-  // `UniqueFunction`, but this works as well. We can't use `std::function`, as
-  // the actions may not be copy constructable.
-  struct IAction {
-    virtual void Run() = 0;
-    virtual ~IAction() = default;
-  };
-  template <typename F>
-  struct Action : IAction {
-    explicit Action(F&& aAction) : mAction(std::move(aAction)) {}
-    void Run() override { mAction(); }
-    F mAction;
-  };
-
   Mutex& mMutex;
-  AutoTArray<UniquePtr<IAction>, 4> mActions;
+  AutoTArray<MoveOnlyFunction<void()>, 4> mActions;
 };
 
 static void DoNotifyOnUnlock(DataPipeAutoLock& aLock,