Display histograms from subprocesses in chrome://histograms

base/metrics/sparse_histogram.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_METRICS_SPARSE_HISTOGRAM_H_
 #define BASE_METRICS_SPARSE_HISTOGRAM_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 63 matching lines @@
   HistogramType GetHistogramType() const override;
   bool HasConstructionArguments(Sample expected_minimum,
                                 Sample expected_maximum,
                                 uint32_t expected_bucket_count) const override;
   void Add(Sample value) override;
   void AddCount(Sample value, int count) override;
   void AddSamples(const HistogramSamples& samples) override;
   bool AddSamplesFromPickle(base::PickleIterator* iter) override;
   std::unique_ptr<HistogramSamples> SnapshotSamples() const override;
   std::unique_ptr<HistogramSamples> SnapshotDelta() override;
-  void WriteHTMLGraph(std::string* output) const override;
-  void WriteAscii(std::string* output) const override;
+  void WriteHTMLGraph(const HistogramSamples* snapshot,
+                      std::string* output) const override;
+  void WriteAscii(const HistogramSamples* snapshot,
+                  std::string* output) const override;
 
  protected:
   // HistogramBase implementation:
   bool SerializeInfoImpl(base::Pickle* pickle) const override;
 
  private:
   // Clients should always use FactoryGet to create SparseHistogram.
   explicit SparseHistogram(const std::string& name);
 
   SparseHistogram(PersistentHistogramAllocator* allocator,
                   const std::string& name,
                   HistogramSamples::Metadata* meta,
                   HistogramSamples::Metadata* logged_meta);
 
   friend BASE_EXPORT HistogramBase* DeserializeHistogramInfo(
       base::PickleIterator* iter);
   static HistogramBase* DeserializeInfoImpl(base::PickleIterator* iter);
 
   void GetParameters(DictionaryValue* params) const override;
   void GetCountAndBucketData(Count* count,
                              int64_t* sum,
                              ListValue* buckets) const override;
 
   // Helpers for emitting Ascii graphic.  Each method appends data to output.
   void WriteAsciiImpl(bool graph_it,
                       const std::string& newline,
+                      const HistogramSamples* snapshot,
                       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;
 
   // Protects access to |samples_|.
   mutable base::Lock lock_;
 
   std::unique_ptr<HistogramSamples> samples_;
   std::unique_ptr<HistogramSamples> logged_samples_;
 
   DISALLOW_COPY_AND_ASSIGN(SparseHistogram);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_SPARSE_HISTOGRAM_H_