Update from https://crrev.com/333737

base/trace_event/memory_allocator_dump_guid.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_MEMORY_ALLOCATOR_DUMP_GUID_H_
+#define BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_GUID_H_
+
+#include <string>
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+
+namespace base {
+namespace trace_event {
+
+class BASE_EXPORT MemoryAllocatorDumpGuid {
+ public:
+  MemoryAllocatorDumpGuid();
+  explicit MemoryAllocatorDumpGuid(uint64 guid);
+
+  // Utility ctor to hash a GUID if the caller prefers a string. The caller
+  // still has to ensure that |guid_str| is unique, per snapshot, within the
+  // global scope of all the traced processes.
+  explicit MemoryAllocatorDumpGuid(const std::string& guid_str);
+
+  // Returns a (hex-encoded) string representation of the guid.
+  std::string ToString() const;
+
+  bool empty() const { return guid_ == 0u; }
+
+  bool operator==(const MemoryAllocatorDumpGuid& other) const {
+    return guid_ == other.guid_;
+  }
+
+  bool operator!=(const MemoryAllocatorDumpGuid& other) const {
+    return !(*this == other);
+  }
+
+ private:
+  uint64 guid_;
+
+  // Deliberately copy-able.
+};
+
+}  // namespace trace_event
+}  // namespace base
+
+#endif  // BASE_TRACE_EVENT_MEMORY_ALLOCATOR_DUMP_GUID_H_