Count m(un)map for each stacktrace in MemoryRegionMap instead of HeapProfileTable.

third_party/tcmalloc/chromium/src/heap-profile-stats.h

+// Copyright (c) 2013 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 HEAP_PROFILE_STATS_H_
+#define HEAP_PROFILE_STATS_H_
+
+class HeapProfileStats {
+public:
+  // Longest stack trace we record.
+  static const int kMaxStackDepth = 32;
+
+  struct Stats {
+    int32 allocs;      // Number of allocation calls
+    int32 frees;       // Number of free calls
+    int64 alloc_size;  // Total size of all allocated objects so far
+    int64 free_size;   // Total size of all freed objects so far
+
+    // semantic equality
+    bool Equivalent(const Stats& x) const {
+      return allocs - frees == x.allocs - x.frees  &&
+             alloc_size - free_size == x.alloc_size - x.free_size;
+    }
+  };
+
+  struct Bucket : public Stats {
+    uintptr_t    hash;   // Hash value of the stack trace
+    int          depth;  // Depth of stack trace
+    const void** stack;  // Stack trace
+    Bucket*      next;   // Next entry in hash-table
+  };
+};
+
+#endif  // HEAP_PROFILE_STATS_H_