Send compressed histograms with system logs when sending feedback.

base/metrics/statistics_recorder.h

Index: base/metrics/statistics_recorder.h
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 0fdfb7698de150248d9dac461d64f417553dc8ac..af45530188456b400522c689305d4c38ad953963 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -54,6 +54,7 @@ class BASE_EXPORT StatisticsRecorder {
   // registered histograms).
   static void WriteHTMLGraph(const std::string& query, std::string* output);
   static void WriteGraph(const std::string& query, std::string* output);
+  static void WriteJSON(const std::string& query, std::string* output);
 
   // Method for extracting histograms which were marked for use by UMA.
   static void GetHistograms(Histograms* output);