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diff --git a/xpcom/base/DarwinObjectPtr.h b/xpcom/base/DarwinObjectPtr.h
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+++ b/xpcom/base/DarwinObjectPtr.h
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+/*
+ * Copyright (C) 2014-2021 Apple Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
+ * THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+// Adapted from
+// https://github.com/WebKit/WebKit/blob/ad340677c00a4b4b6a299c93a6e18cd073b3f4e9/Source/WTF/wtf/OSObjectPtr.h
+
+#ifndef mozilla_DarwinObjectPtr_h
+#define mozilla_DarwinObjectPtr_h
+
+#include <os/object.h>
+#include <utility>
+#include "mozilla/Attributes.h"
+
+// Because ARC enablement is a compile-time choice, and we compile this header
+// both ways, we need a separate copy of our code when ARC is enabled.
+#if __has_feature(objc_arc)
+#  define AdoptDarwinObject AdoptDarwinObjectArc
+#  define RetainDarwinObject RetainDarwinObjectArc
+#  define ReleaseDarwinObject ReleaseDarwinObjectArc
+#endif
+
+namespace mozilla {
+
+template <typename>
+class DarwinObjectPtr;
+template <typename T>
+[[nodiscard]] DarwinObjectPtr<T> AdoptDarwinObject(T);
+
+template <typename T>
+static inline void RetainDarwinObject(T aPtr) {
+#if !__has_feature(objc_arc)
+  os_retain(aPtr);
+#endif
+}
+
+template <typename T>
+static inline void ReleaseDarwinObject(T aPtr) {
+#if !__has_feature(objc_arc)
+  os_release(aPtr);
+#endif
+}
+
+template <typename T>
+class DarwinObjectPtr {
+ public:
+  DarwinObjectPtr() : mPtr(nullptr) {}
+
+  ~DarwinObjectPtr() {
+    if (mPtr) {
+      ReleaseDarwinObject(mPtr);
+    }
+  }
+
+  T get() const { return mPtr; }
+
+  explicit operator bool() const { return mPtr; }
+  bool operator!() const { return !mPtr; }
+
+  DarwinObjectPtr(const DarwinObjectPtr& aOther) : mPtr(aOther.mPtr) {
+    if (mPtr) {
+      RetainDarwinObject(mPtr);
+    }
+  }
+
+  DarwinObjectPtr(DarwinObjectPtr&& aOther) : mPtr(std::move(aOther.mPtr)) {
+    aOther.mPtr = nullptr;
+  }
+
+  MOZ_IMPLICIT DarwinObjectPtr(T aPtr) : mPtr(std::move(aPtr)) {
+    if (mPtr) {
+      RetainDarwinObject(mPtr);
+    }
+  }
+
+  DarwinObjectPtr& operator=(const DarwinObjectPtr& aOther) {
+    DarwinObjectPtr ptr = aOther;
+    swap(ptr);
+    return *this;
+  }
+
+  DarwinObjectPtr& operator=(DarwinObjectPtr&& aOther) {
+    DarwinObjectPtr ptr = std::move(aOther);
+    swap(ptr);
+    return *this;
+  }
+
+  DarwinObjectPtr& operator=(std::nullptr_t) {
+    if (mPtr) {
+      ReleaseDarwinObject(mPtr);
+    }
+    mPtr = nullptr;
+    return *this;
+  }
+
+  DarwinObjectPtr& operator=(T aOther) {
+    DarwinObjectPtr ptr = std::move(aOther);
+    swap(ptr);
+    return *this;
+  }
+
+  void swap(DarwinObjectPtr& aOther) { std::swap(mPtr, aOther.mPtr); }
+
+  [[nodiscard]] T forget() { return std::exchange(mPtr, nullptr); }
+
+  friend DarwinObjectPtr AdoptDarwinObject<T>(T);
+
+ private:
+  struct AdoptDarwinObjectTag {};
+  DarwinObjectPtr(AdoptDarwinObjectTag, T aPtr) : mPtr(std::move(aPtr)) {}
+
+  T mPtr;
+};
+
+template <typename T>
+inline DarwinObjectPtr<T> AdoptDarwinObject(T aPtr) {
+  return DarwinObjectPtr<T>{typename DarwinObjectPtr<T>::AdoptDarwinObjectTag{},
+                            std::move(aPtr)};
+}
+
+}  // namespace mozilla
+
+#endif