Add simple non-response-based question parsing for mDNS passive listening

net/dns/dns_response.h

Index: net/dns/dns_response.h
diff --git a/net/dns/dns_response.h b/net/dns/dns_response.h
index 78fb73571028ad6fa3e47d2f81eaf1516e373372..4a445d967aac11cbc651a42174378b04ed1b1be6 100644
--- a/net/dns/dns_response.h
+++ b/net/dns/dns_response.h
@@ -67,6 +67,9 @@ class NET_EXPORT_PRIVATE DnsRecordParser {
   // Parses the next resource record into |record|. Returns true if succeeded.
   bool ReadRecord(DnsResourceRecord* record);
 
+  // Skip a question section, returns true if succeeded.
+  bool SkipQuestion();
+
  private:
   const char* packet_;
   size_t length_;
@@ -115,6 +118,10 @@ class NET_EXPORT_PRIVATE DnsResponse {
   // packet matches the |query| id and question.
   bool InitParse(int nbytes, const DnsQuery& query);
 
+  // Assuming the internal buffer holds |nbytes| bytes, initialize the parser
+  // without matching it against an existing query.
+  bool InitParseWithoutQuery(int nbytes);
+
   // Returns true if response is valid, that is, after successful InitParse.
   bool IsValid() const;