Implement write methods for SparseHistogram

base/metrics/sparse_histogram.h

Index: base/metrics/sparse_histogram.h
diff --git a/base/metrics/sparse_histogram.h b/base/metrics/sparse_histogram.h
index 9c207666e5d04c21fa97978438617827b7a4085f..4de200254a95416e6a33f859f19957aab342ed12 100644
--- a/base/metrics/sparse_histogram.h
+++ b/base/metrics/sparse_histogram.h
@@ -90,6 +90,15 @@ class BASE_EXPORT_PRIVATE SparseHistogram : public HistogramBase {
   virtual void GetCountAndBucketData(Count* count,
                                      ListValue* buckets) const OVERRIDE;
 
+  // Helpers for emitting Ascii graphic.  Each method appends data to output.
+  void WriteAsciiImpl(bool graph_it,
+                      const std::string& newline,
+                      std::string* output) const;
+
+  // Write a common header message describing this histogram.
+  void WriteAsciiHeader(const Count total_count,
+                        std::string* output) const;
+
   // For constuctor calling.
   friend class SparseHistogramTest;