1 files changed, 9 insertions, 0 deletions
diff --git a/chrome/common/histogram_synchronizer.h b/chrome/common/histogram_synchronizer.h
index ed866fc..29c34e2 100644
--- a/chrome/common/histogram_synchronizer.h
+++ b/chrome/common/histogram_synchronizer.h
@@ -32,6 +32,15 @@ class HistogramSynchronizer : public
     SYNCHRONOUS_HISTOGRAMS
   };
 
+  // We reserve 0 through 9 sequence numbers for special purposes. For example,
+  // sequence number 0 is used by renderer to send its histograms before it
+  // closing renderer. We wanted to reserve the rest of sequence numbers for
+  // future purposes.
+  enum SequenceNumbers {
+    RENDERER_CLOSING_SEQUENCE_NUMBER = 0,
+    STARTING_SEQUENCE_NUMBER = 10
+  };
+
   HistogramSynchronizer();
 
   ~HistogramSynchronizer();