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diff --git a/mozglue/baseprofiler/core/ProfilerBacktrace.h b/mozglue/baseprofiler/core/ProfilerBacktrace.h
new file mode 100644
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+++ b/mozglue/baseprofiler/core/ProfilerBacktrace.h
@@ -0,0 +1,162 @@
+/* -*- Mode: C++; tab-width: 2; 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 __PROFILER_BACKTRACE_H
+#define __PROFILER_BACKTRACE_H
+
+#include "mozilla/ProfileChunkedBuffer.h"
+#include "mozilla/UniquePtr.h"
+
+#include <string>
+
+namespace mozilla {
+
+class TimeStamp;
+
+namespace baseprofiler {
+
+class ProfileBuffer;
+class SpliceableJSONWriter;
+class ThreadInfo;
+class UniqueStacks;
+
+// ProfilerBacktrace encapsulates a synchronous sample.
+// It can work with a ProfileBuffer and/or a ProfileChunkedBuffer (if both, they
+// must already be linked together). The ProfileChunkedBuffer contains all the
+// data; the ProfileBuffer is not strictly needed, only provide it if it is
+// already available at the call site.
+// And these buffers can either be:
+// - owned here, so that the ProfilerBacktrace object can be kept for later
+//   use), OR
+// - referenced through pointers (in cases where the backtrace is immediately
+//   streamed out, so we only need temporary references to external buffers);
+//   these pointers may be null for empty backtraces.
+class ProfilerBacktrace {
+ public:
+  // Take ownership of external buffers and use them to keep, and to stream a
+  // backtrace. If a ProfileBuffer is given, its underlying chunked buffer must
+  // be provided as well.
+  explicit ProfilerBacktrace(
+      const char* aName,
+      UniquePtr<ProfileChunkedBuffer> aProfileChunkedBufferStorage,
+      UniquePtr<ProfileBuffer> aProfileBufferStorageOrNull = nullptr);
+
+  // Take pointers to external buffers and use them to stream a backtrace.
+  // If null, the backtrace is effectively empty.
+  // If both are provided, they must already be connected.
+  explicit ProfilerBacktrace(
+      const char* aName,
+      ProfileChunkedBuffer* aExternalProfileChunkedBufferOrNull = nullptr,
+      ProfileBuffer* aExternalProfileBufferOrNull = nullptr);
+
+  ~ProfilerBacktrace();
+
+  [[nodiscard]] bool IsEmpty() const {
+    return !mProfileChunkedBuffer ||
+           ProfileBufferEntryWriter::Serializer<ProfileChunkedBuffer>::Bytes(
+               *mProfileChunkedBuffer) <= ULEB128Size(0u);
+  }
+
+  // ProfilerBacktraces' stacks are deduplicated in the context of the
+  // profile that contains the backtrace as a marker payload.
+  //
+  // That is, markers that contain backtraces should not need their own stack,
+  // frame, and string tables. They should instead reuse their parent
+  // profile's tables.
+  BaseProfilerThreadId StreamJSON(SpliceableJSONWriter& aWriter,
+                                  const TimeStamp& aProcessStartTime,
+                                  UniqueStacks& aUniqueStacks);
+
+ private:
+  // Used to de/serialize a ProfilerBacktrace.
+  friend ProfileBufferEntryWriter::Serializer<ProfilerBacktrace>;
+  friend ProfileBufferEntryReader::Deserializer<ProfilerBacktrace>;
+
+  std::string mName;
+
+  // `ProfileChunkedBuffer` in which `mProfileBuffer` stores its data; must be
+  // located before `mProfileBuffer` so that it's destroyed after.
+  UniquePtr<ProfileChunkedBuffer> mOptionalProfileChunkedBufferStorage;
+  // If null, there is no need to check mProfileBuffer's (if present) underlying
+  // buffer because this is done when constructed.
+  ProfileChunkedBuffer* mProfileChunkedBuffer;
+
+  UniquePtr<ProfileBuffer> mOptionalProfileBufferStorage;
+  ProfileBuffer* mProfileBuffer;
+};
+
+}  // namespace baseprofiler
+
+// Format: [ UniquePtr<BlockRingsBuffer> | name ]
+// Initial len==0 marks a nullptr or empty backtrace.
+template <>
+struct ProfileBufferEntryWriter::Serializer<baseprofiler::ProfilerBacktrace> {
+  static Length Bytes(const baseprofiler::ProfilerBacktrace& aBacktrace) {
+    if (!aBacktrace.mProfileChunkedBuffer) {
+      // No buffer.
+      return ULEB128Size(0u);
+    }
+    auto bufferBytes = SumBytes(*aBacktrace.mProfileChunkedBuffer);
+    if (bufferBytes <= ULEB128Size(0u)) {
+      // Empty buffer.
+      return ULEB128Size(0u);
+    }
+    return bufferBytes + SumBytes(aBacktrace.mName);
+  }
+
+  static void Write(ProfileBufferEntryWriter& aEW,
+                    const baseprofiler::ProfilerBacktrace& aBacktrace) {
+    if (!aBacktrace.mProfileChunkedBuffer ||
+        SumBytes(*aBacktrace.mProfileChunkedBuffer) <= ULEB128Size(0u)) {
+      // No buffer, or empty buffer.
+      aEW.WriteULEB128(0u);
+      return;
+    }
+    aEW.WriteObject(*aBacktrace.mProfileChunkedBuffer);
+    aEW.WriteObject(aBacktrace.mName);
+  }
+};
+
+template <typename Destructor>
+struct ProfileBufferEntryWriter::Serializer<
+    UniquePtr<baseprofiler::ProfilerBacktrace, Destructor>> {
+  static Length Bytes(const UniquePtr<baseprofiler::ProfilerBacktrace,
+                                      Destructor>& aBacktrace) {
+    if (!aBacktrace) {
+      // Null backtrace pointer (treated like an empty backtrace).
+      return ULEB128Size(0u);
+    }
+    return SumBytes(*aBacktrace);
+  }
+
+  static void Write(ProfileBufferEntryWriter& aEW,
+                    const UniquePtr<baseprofiler::ProfilerBacktrace,
+                                    Destructor>& aBacktrace) {
+    if (!aBacktrace) {
+      // Null backtrace pointer (treated like an empty backtrace).
+      aEW.WriteULEB128(0u);
+      return;
+    }
+    aEW.WriteObject(*aBacktrace);
+  }
+};
+
+template <typename Destructor>
+struct ProfileBufferEntryReader::Deserializer<
+    UniquePtr<baseprofiler::ProfilerBacktrace, Destructor>> {
+  static void ReadInto(
+      ProfileBufferEntryReader& aER,
+      UniquePtr<baseprofiler::ProfilerBacktrace, Destructor>& aBacktrace) {
+    aBacktrace = Read(aER);
+  }
+
+  static UniquePtr<baseprofiler::ProfilerBacktrace, Destructor> Read(
+      ProfileBufferEntryReader& aER);
+};
+
+}  // namespace mozilla
+
+#endif  // __PROFILER_BACKTRACE_H