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diff --git a/js/src/ds/TraceableFifo.h b/js/src/ds/TraceableFifo.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+#ifndef js_TraceableFifo_h
+#define js_TraceableFifo_h
+
+#include "ds/Fifo.h"
+#include "js/RootingAPI.h"
+#include "js/TracingAPI.h"
+
+namespace js {
+
+// A TraceableFifo is a Fifo with an additional trace method that knows how to
+// visit all of the items stored in the Fifo. For Fifos that contain GC things,
+// this is usually more convenient than manually iterating and marking the
+// contents.
+//
+// Most types of GC pointers as keys and values can be traced with no extra
+// infrastructure. For structs and non-gc-pointer members, ensure that there is
+// a specialization of GCPolicy<T> with an appropriate trace method available
+// to handle the custom type. Generic helpers can be found in
+// js/public/TracingAPI.h. Generic helpers can be found in
+// js/public/TracingAPI.h.
+//
+// Note that although this Fifo's trace will deal correctly with moved items, it
+// does not itself know when to barrier or trace items. To function properly it
+// must either be used with Rooted, or barriered and traced manually.
+template <typename T, size_t MinInlineCapacity = 0,
+          typename AllocPolicy = TempAllocPolicy>
+class TraceableFifo : public js::Fifo<T, MinInlineCapacity, AllocPolicy> {
+  using Base = js::Fifo<T, MinInlineCapacity, AllocPolicy>;
+
+ public:
+  explicit TraceableFifo(AllocPolicy alloc = AllocPolicy())
+      : Base(std::move(alloc)) {}
+
+  TraceableFifo(TraceableFifo&& rhs) : Base(std::move(rhs)) {}
+  TraceableFifo& operator=(TraceableFifo&& rhs) = default;
+
+  TraceableFifo(const TraceableFifo&) = delete;
+  TraceableFifo& operator=(const TraceableFifo&) = delete;
+
+  void trace(JSTracer* trc) {
+    for (size_t i = 0; i < this->front_.length(); ++i) {
+      JS::GCPolicy<T>::trace(trc, &this->front_[i], "fifo element");
+    }
+    for (size_t i = 0; i < this->rear_.length(); ++i) {
+      JS::GCPolicy<T>::trace(trc, &this->rear_[i], "fifo element");
+    }
+  }
+};
+
+template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
+class WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>, Wrapper> {
+  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
+  const TF& fifo() const { return static_cast<const Wrapper*>(this)->get(); }
+
+ public:
+  size_t length() const { return fifo().length(); }
+  bool empty() const { return fifo().empty(); }
+  const T& front() const { return fifo().front(); }
+};
+
+template <typename Wrapper, typename T, size_t Capacity, typename AllocPolicy>
+class MutableWrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
+                                  Wrapper>
+    : public WrappedPtrOperations<TraceableFifo<T, Capacity, AllocPolicy>,
+                                  Wrapper> {
+  using TF = TraceableFifo<T, Capacity, AllocPolicy>;
+  TF& fifo() { return static_cast<Wrapper*>(this)->get(); }
+
+ public:
+  T& front() { return fifo().front(); }
+
+  template <typename U>
+  bool pushBack(U&& u) {
+    return fifo().pushBack(std::forward<U>(u));
+  }
+  template <typename... Args>
+  bool emplaceBack(Args&&... args) {
+    return fifo().emplaceBack(std::forward<Args...>(args...));
+  }
+
+  void popFront() { fifo().popFront(); }
+  void clear() { fifo().clear(); }
+};
+
+}  // namespace js
+
+#endif  // js_TraceableFifo_h