NOT FOR REVIEW - Slow Reports Reference Implementation

base/metrics/histogram_base.h

Index: base/metrics/histogram_base.h
diff --git a/base/metrics/histogram_base.h b/base/metrics/histogram_base.h
index c24df248112cc5fd99d339278f1c8c3404239891..4a51b5535aa12fb5506f477f3b939aaf80fbbc47 100644
--- a/base/metrics/histogram_base.h
+++ b/base/metrics/histogram_base.h
@@ -13,6 +13,7 @@
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_piece.h"
 #include "base/time/time.h"
@@ -145,6 +146,9 @@ class BASE_EXPORT HistogramBase {
   // customize the output.
   void WriteJSON(std::string* output) const;
 
+  typedef base::Callback<void(void)> ModifiedCallback;
+  void SetCallback(const ModifiedCallback&);
+
  protected:
   // Subclasses should implement this function to make SerializeInfo work.
   virtual bool SerializeInfoImpl(Pickle* pickle) const = 0;
@@ -173,6 +177,8 @@ class BASE_EXPORT HistogramBase {
                              double scaled_sum,
                              std::string* output) const;
 
+  ModifiedCallback callback_;
+
  private:
   const std::string histogram_name_;
   int32_t flags_;