1 files changed, 32 insertions, 5 deletions

diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index b523057596..b1d182e93e 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -10,20 +10,23 @@
 #ifndef BASE_METRICS_STATISTICS_RECORDER_H_
 #define BASE_METRICS_STATISTICS_RECORDER_H_
 
+#include <stdint.h>
+
 #include <list>
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/base_export.h"
-#include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "base/metrics/histogram_base.h"
 
 namespace base {
 
 class BucketRanges;
-class HistogramBase;
 class Lock;
 
 class BASE_EXPORT StatisticsRecorder {
@@ -75,14 +78,37 @@ class BASE_EXPORT StatisticsRecorder {
   // histograms).
   static void GetSnapshot(const std::string& query, Histograms* snapshot);
 
+  typedef base::Callback<void(HistogramBase::Sample)> OnSampleCallback;
+
+  // SetCallback sets the callback to notify when a new sample is recorded on
+  // the histogram referred to by |histogram_name|. The call to this method can
+  // be be done before or after the histogram is created. This method is thread
+  // safe. The return value is whether or not the callback was successfully set.
+  static bool SetCallback(const std::string& histogram_name,
+                          const OnSampleCallback& callback);
+
+  // ClearCallback clears any callback set on the histogram referred to by
+  // |histogram_name|. This method is thread safe.
+  static void ClearCallback(const std::string& histogram_name);
+
+  // FindCallback retrieves the callback for the histogram referred to by
+  // |histogram_name|, or a null callback if no callback exists for this
+  // histogram. This method is thread safe.
+  static OnSampleCallback FindCallback(const std::string& histogram_name);
+
  private:
-  // We keep all registered histograms in a map, from name to histogram.
-  typedef std::map<std::string, HistogramBase*> HistogramMap;
+  // We keep all registered histograms in a map, indexed by the hash of the
+  // name of the histogram.
+  typedef std::map<uint64_t, HistogramBase*> HistogramMap;
+
+  // We keep a map of callbacks to histograms, so that as histograms are
+  // created, we can set the callback properly.
+  typedef std::map<std::string, OnSampleCallback> CallbackMap;
 
   // We keep all |bucket_ranges_| in a map, from checksum to a list of
   // |bucket_ranges_|.  Checksum is calculated from the |ranges_| in
   // |bucket_ranges_|.
-  typedef std::map<uint32, std::list<const BucketRanges*>*> RangesMap;
+  typedef std::map<uint32_t, std::list<const BucketRanges*>*> RangesMap;
 
   friend struct DefaultLazyInstanceTraits<StatisticsRecorder>;
   friend class HistogramBaseTest;
@@ -103,6 +129,7 @@ class BASE_EXPORT StatisticsRecorder {
   static void DumpHistogramsToVlog(void* instance);
 
   static HistogramMap* histograms_;
+  static CallbackMap* callbacks_;
   static RangesMap* ranges_;
 
   // Lock protects access to above maps.