[Tracing] Make heap profiler type info a string

base/trace_event/heap_profiler_type_name_deduplicator.h

+// Copyright 2015 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 BASE_TRACE_EVENT_HEAP_PROFILER_TYPE_NAME_DEDUPLICATOR_H_
+#define BASE_TRACE_EVENT_HEAP_PROFILER_TYPE_NAME_DEDUPLICATOR_H_
+
+#include <map>
+#include <string>
+
+#include "base/base_export.h"
+#include "base/macros.h"
+#include "base/trace_event/trace_event_impl.h"
+
+namespace base {
+namespace trace_event {
+
+class TraceEventMemoryOverhead;
+
+// Data structure that assigns a unique numeric ID to |const char*|s.
+class BASE_EXPORT TypeNameDeduplicator : public ConvertableToTraceFormat {
+ public:
+  TypeNameDeduplicator();
+
+  // Inserts a type name and returns its ID.
+  int Insert(const char* type_name);
+
+  // Estimates memory overhead including |sizeof(TypeNameDeduplicator)|.
+  void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead) override;
+
+ private:
+  ~TypeNameDeduplicator() override;
+
+  // Writes the type ID -> type name mapping to the trace log.
+  void AppendAsTraceFormat(std::string* out) const override;
+
+  // Map from type name to type ID.
+  std::map<const char*, int> type_ids_;
+
+  DISALLOW_COPY_AND_ASSIGN(TypeNameDeduplicator);
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_HEAP_PROFILER_TYPE_NAME_DEDUPLICATOR_H_