Randomly select a single rappor sample when more than one is collected.

components/rappor/rappor_metric.h

 // Copyright 2014 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 COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
 #define COMPONENTS_RAPPOR_RAPPOR_METRIC_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 17 matching lines @@
   // Takes the |metric_name| that this will be reported to the server with,
   // a |parameters| describing size and probability weights used in recording
   // this metric, and a |cohort| value, which determines the hash functions
   // used in the Bloom filter.
   RapporMetric(const std::string& metric_name,
                const RapporParameters& parameters,
                int32_t cohort);
   ~RapporMetric();
 
   // Records an additional sample in the Bloom filter.
+  // A random sample will be used when reporting this metric.

[Alexei Svitkine (slow), 2014/08/05 13:22:05]

Nit: expand comment to mention "when more than one sample is added for the same
metric"

[Steven Holte, 2014/08/05 20:32:32]

Done.

   void AddSample(const std::string& str);
 
   // Retrieves the current Bloom filter bits.
   const ByteVector& bytes() const { return bloom_filter_.bytes(); }
 
   // Gets the parameter values this metric was constructed with.
   const RapporParameters& parameters() const { return parameters_; }
 
   // Generates the bits to report for this metric.  Using the secret as a seed,
   // randomly selects bits for redaction.  Then flips coins to generate the
   // final report bits.
   ByteVector GetReport(const std::string& secret) const;
 
+  // Specify the bytes to generate a report from, for testing purposes.
+  void SetBytesForTesting(const ByteVector& bytes);
+
  private:
   const std::string metric_name_;
   const RapporParameters parameters_;
+  uint32_t sample_count_;
   BloomFilter bloom_filter_;
 
   DISALLOW_COPY_AND_ASSIGN(RapporMetric);
 };
 
 }  // namespace rappor
 
 #endif  // COMPONENTS_RAPPOR_RAPPOR_METRIC_H_