Modify rappor parameters.

components/rappor/rappor_metric.cc

Index: components/rappor/rappor_metric.cc
diff --git a/components/rappor/rappor_metric.cc b/components/rappor/rappor_metric.cc
index f8ff16252e232ddbdbd258e6f337ed20b3d124f2..b4bd950af9d1741210b81dcdf54bbd893b1b63b2 100644
--- a/components/rappor/rappor_metric.cc
+++ b/components/rappor/rappor_metric.cc
@@ -10,13 +10,15 @@ namespace rappor {
 
 RapporMetric::RapporMetric(const std::string& metric_name,
                            const RapporParameters& parameters,
-                           int32_t cohort)
+                           int32_t cohort_seed)
     : metric_name_(metric_name),
       parameters_(parameters),
       bloom_filter_(parameters.bloom_filter_size_bytes,
                     parameters.bloom_filter_hash_function_count,
-                    cohort * parameters.bloom_filter_hash_function_count) {
-  DCHECK_GE(cohort, 0);
+                    (cohort_seed % parameters.num_cohorts) *

[ulfar, 2014/05/27 17:52:14]

This is the only place where I see parameters.num_cohorts being used.  In
particular, I didn't see anyplace where the actual cohort number (mod
num_cohorts) is being reported to the service.  Is the cohort_seed now being
reported to the service, and the service is expected to do the modulus before
analysis?

[Steven Holte, 2014/05/27 17:58:42]

Yes, it's reporting the seed, and we'll just aggregate over the modulus in the
analysis.

+                        parameters.bloom_filter_hash_function_count) {
+  DCHECK_GE(cohort_seed, 0);
+  DCHECK_LT(cohort_seed, RapporParameters::kMaxCohorts);
 }
 
 RapporMetric::~RapporMetric() {}