Add a switch to emit browser histograms.

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..0716e80572d4e314e537a7400e9f8fab294f32e1 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -49,12 +49,16 @@ class BASE_EXPORT StatisticsRecorder {
   static const BucketRanges* RegisterOrDeleteDuplicateRanges(
       const BucketRanges* ranges);
 
-  // Methods for printing histograms.  Only histograms which have query as
-  // a substring are written to output (an empty string will process all
-  // registered histograms).
+  // Methods for appending histogram data to a string.  Only histograms which
+  // have |query| as a substring are written to |output| (an empty string will
+  // process all registered histograms).
   static void WriteHTMLGraph(const std::string& query, std::string* output);
   static void WriteGraph(const std::string& query, std::string* output);
 
+  // Returns the histograms with |query| as a substring as JSON text (an empty
+  // |query| will process all registered histograms).
+  static std::string ToJSON(const std::string& query);
+
   // Method for extracting histograms which were marked for use by UMA.
   static void GetHistograms(Histograms* output);