Adds a method to the Performance Monitor Database to fetch the most recent metric.

chrome/browser/performance_monitor/database.cc

Index: chrome/browser/performance_monitor/database.cc
diff --git a/chrome/browser/performance_monitor/database.cc b/chrome/browser/performance_monitor/database.cc
index 8eb135080a00cedf9b51c82893712d7fc4520b0b..8cb2dbf4a2cdcce47d99d9282e8cae10c8039fb2 100644
--- a/chrome/browser/performance_monitor/database.cc
+++ b/chrome/browser/performance_monitor/database.cc
@@ -379,6 +379,29 @@ std::vector<std::string> Database::GetActiveActivities(
   return results;
 }
 
+bool Database::GetRecentStatsForActivityAndMetric(
+    const std::string& activity,
+    MetricType metric,
+    MetricInfo* info) {
+  CHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  std::string recent_map_key = CreateRecentMapKey(metric, activity);
+  if (!recent_map_.count(recent_map_key))
+    return false;
+  std::string recent_start_key = recent_map_[recent_map_key];

[eaugusti, 2012/07/31 18:46:06]

Not really a "start" key, just a key.

[chebert, 2012/07/31 19:26:36]

Done.

+
+  scoped_ptr<leveldb::Iterator> it(recent_db_->NewIterator(read_options_));

[eaugusti, 2012/07/31 18:46:06]

Maybe use Get() instead of an iterator:
http://leveldb.googlecode.com/svn/trunk/doc/index.html

You will have to check, but I think that it will return a status !s.ok() if the
key doesn't exist.

[chebert, 2012/07/31 19:26:36]

Done.

+
+  it->Seek(recent_start_key);
+  if (it->Valid()) {
+    RecentKey split_key = SplitRecentKey(it->key().ToString());
+    if (split_key.activity == activity) {
+      *info = MetricInfo(split_key.time, it->value().ToString());
+      return true;
+    }
+  }
+  return false;
+}
+
 Database::MetricInfoVector Database::GetStatsForActivityAndMetric(
     const std::string& activity, MetricType metric_type,
     const base::Time& start, const base::Time& end) {