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 {

[Alexander Potapenko, 2013/03/07 06:48:38]

A class with no members and no methods, huh? Maybe use a namespace instead?

[Dai Mikurube (NOT FULLTIME), 2013/03/07 12:32:16]

Hmm, agreed.  I had other methods in my local changes, but I removed them.

Finally, I made them HeapProfileStats and HeapProfileBucket like other classes
such as HeapProfileTable in heap-profile-table.h.

+public:

[Alexander Potapenko, 2013/03/07 06:48:38]

1-space indentation.

[Dai Mikurube (NOT FULLTIME), 2013/03/07 12:32:16]

It's unnecessary now because of the change above.

+  // Longest stack trace we record.
+  static const int kMaxStackDepth = 32;

[Alexander Potapenko, 2013/03/07 06:48:38]

Is that enough? Webkit stacks may have up to 250 frames.

[Dai Mikurube (NOT FULLTIME), 2013/03/07 12:32:16]

It's the default of TCMalloc's original value.  We may want more if required,
but it's enough for now.

+
+  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

[Alexander Potapenko, 2013/03/07 06:48:38]

Please fix the comment.
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Punctu...

[Dai Mikurube (NOT FULLTIME), 2013/03/07 12:32:16]

Done.

+    bool Equivalent(const Stats& x) const {
+      return allocs - frees == x.allocs - x.frees  &&

[Alexander Potapenko, 2013/03/07 06:48:38]

Please remove the extra space before &&.

[Dai Mikurube (NOT FULLTIME), 2013/03/07 12:32:16]

Done.

+             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_