Record call site history in LeakDetectorImpl

components/metrics/leak_detector/ranked_set.cc

 // 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.
 
 #include "components/metrics/leak_detector/ranked_set.h"
 
 #include <algorithm>
 
 namespace metrics {
 namespace leak_detector {
@@ skipping 30 matching lines @@
   new_entry.count = count;
   entries_.insert(new_entry);
 
   // Limit the container size if it exceeds the maximum allowed size, by
   // deleting the last element. This should only iterate once because the size
   // can only have increased by 1, but use a while loop just to be safe.
   while (entries_.size() > max_size_)
     entries_.erase(--entries_.end());
 }
 
+RankedSet::const_iterator RankedSet::Find(const ValueType& value) const {
+  // Due to the unusual way the entries are stored, it is best to manually
+  // iterate through them until an entry with a matching value is found.
+  // e.g. std::find() would not work because it depends on exact matching by the
+  // whole Entry struct.

[Will Harris, 2016/04/09 20:10:23]

can't you just implement the operators in Entry rather than implementing Find?

[Simon Que, 2016/04/09 21:04:11]

The operator would have to look something like:

  bool operator==(const Entry& other) const {
    return value == other.value && count == other.count;
  }

However, in this case we don't know the count. The alternative would be to have
an == operator that compares |value| only, but it would be strange to someone
looking at the code.

[Will Harris, 2016/04/11 17:26:37]

I think as long as it's commented (perhaps explain what specifically is
"unusual") then it'll be fine. thanks.

[Simon Que, 2016/04/11 18:41:08]

Done.

+  for (const_iterator iter = begin(); iter != end(); ++iter) {
+    if (iter->value == value)
+      return iter;
+  }
+  return end();
+}
+
 }  // namespace leak_detector
 }  // namespace metrics