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

components/rappor/rappor_metric_unittest.cc

Index: components/rappor/rappor_metric_unittest.cc
diff --git a/components/rappor/rappor_metric_unittest.cc b/components/rappor/rappor_metric_unittest.cc
index b5707cf3aa7f0f0464d6f6631a638784a2deed22..25b0432a6326df2a67b8bd008113693dd826d9ed 100644
--- a/components/rappor/rappor_metric_unittest.cc
+++ b/components/rappor/rappor_metric_unittest.cc
@@ -49,10 +49,12 @@ TEST(RapporMetricTest, GetReport) {
 TEST(RapporMetricTest, GetReportStatistics) {
   RapporMetric metric("MyStatsRappor", kTestStatsRapporParameters, 0);
 
-  for (char i = 0; i < 50; i++) {
-    metric.AddSample(base::StringPrintf("%d", i));
+  ByteVector real_bits(kTestStatsRapporParameters.bloom_filter_size_bytes);
+  // Set 152 bits (19 bytes)
+  for (char i = 0; i < 19; i++) {
+    real_bits[i] = 0xff;
   }
-  const ByteVector real_bits = metric.bytes();
+  metric.SetBytesForTesting(real_bits);
   const int real_bit_count = CountBits(real_bits);
   EXPECT_EQ(real_bit_count, 152);