Record call site history in LeakDetectorImpl

components/metrics/leak_detector/ranked_set.cc

Index: components/metrics/leak_detector/ranked_set.cc
diff --git a/components/metrics/leak_detector/ranked_set.cc b/components/metrics/leak_detector/ranked_set.cc
index 5725fb5c01c83cb6f2a0c456096402375c032355..f8945d7014030ee250d1280eeeafa0e96154ed86 100644
--- a/components/metrics/leak_detector/ranked_set.cc
+++ b/components/metrics/leak_detector/ranked_set.cc
@@ -48,5 +48,20 @@ void RankedSet::Add(const ValueType& value, int count) {
     entries_.erase(--entries_.end());
 }
 
+RankedSet::const_iterator RankedSet::Find(const ValueType& value) const {
+  // The entries are stored sorted by |count|, but this function looks for an
+  // entry with a particular |value| field. Thus, std::set::find() will not
+  // work. Nor would std::find(), which matches by both |count| and |value| --
+  // the count is unknown to the caller of this function.
+  //
+  // The most straightforward way is to iterate through the set until a matching
+  // value is found.
+  for (const_iterator iter = begin(); iter != end(); ++iter) {
+    if (iter->value == value)
+      return iter;
+  }
+  return end();
+}
+
 }  // namespace leak_detector
 }  // namespace metrics