Add out-of-process memory logging stream parsing.

chrome/profiling/backtrace_storage.h

Index: chrome/profiling/backtrace_storage.h
diff --git a/chrome/profiling/backtrace_storage.h b/chrome/profiling/backtrace_storage.h
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index 0000000000000000000000000000000000000000..a3d735868f570b4b6230624d4803be1452fca629
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+++ b/chrome/profiling/backtrace_storage.h
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+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_PROFILING_BACKTRACE_STORAGE_H_
+#define CHROME_PROFILING_BACKTRACE_STORAGE_H_
+
+#include <unordered_set>
+#include <vector>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "chrome/profiling/backtrace.h"
+
+namespace profiling {
+
+// This class is threadsafe.
+class BacktraceStorage {
+ public:
+  using Container = std::unordered_set<Backtrace>;
+  using Key = Container::iterator;
+
+  BacktraceStorage();
+  ~BacktraceStorage();
+
+  // Adds the given backtrace to the storage and returns a key to it. If a
+  // matching backtrace already exists, a key to the existing one will be
+  // returned.
+  //
+  // The returned key will have a reference count associated with it, call
+  // Free when the key is no longer needed.
+  Key Insert(std::vector<Address>&& bt);
+
+  // Frees one reference to a backtrace.
+  void Free(const Key& key);
+  void Free(const std::vector<Key>& keys);
+
+  // Returns the backtrace associated with the given key. Assumes the caller
+  // holds a key to it that will keep the backtrace in scope.
+  const Backtrace& GetBacktraceForKey(const Key& key) const;
+
+ private:
+  mutable base::Lock lock_;
+
+  // List of live backtraces for de-duping. Protected by the lock_.
+  Container backtraces_;
+};
+
+}  // namespace profiling
+
+#endif  // CHROME_PROFILING_BACKTRACE_STORAGE_H_