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

components/rappor/bloom_filter.cc

Index: components/rappor/bloom_filter.cc
diff --git a/components/rappor/bloom_filter.cc b/components/rappor/bloom_filter.cc
index d3f9e6339328714bc301237173e4f93baee96fee..9ad8f3ca0ce9d68191e8896229dbf3d44c2e1fcc 100644
--- a/components/rappor/bloom_filter.cc
+++ b/components/rappor/bloom_filter.cc
@@ -20,7 +20,10 @@ BloomFilter::BloomFilter(uint32_t bytes_size,
 
 BloomFilter::~BloomFilter() {}
 
-void BloomFilter::AddString(const std::string& str) {
+void BloomFilter::SetString(const std::string& str) {
+  for (size_t i = 0; i < bytes_.size(); ++i) {
+    bytes_[i] = 0;
+  }
   for (size_t i = 0; i < hash_function_count_; ++i) {
     // Using CityHash here because we have support for it in Dremel.  Many hash
     // functions, such as MD5, SHA1, or Murmur, would probably also work.
@@ -33,4 +36,11 @@ void BloomFilter::AddString(const std::string& str) {
   }
 }
 
+void BloomFilter::SetBytesForTesting(const ByteVector& bytes) {
+  DCHECK_EQ(bytes_.size(), bytes.size());
+  for (size_t i = 0; i < bytes_.size(); ++i) {
+    bytes_[i] = bytes[i];
+  }
+}
+
 }  // namespace rappor