Joins Cookie header components correctly.

net/quic/spdy_utils.cc

Index: net/quic/spdy_utils.cc
diff --git a/net/quic/spdy_utils.cc b/net/quic/spdy_utils.cc
index 78f6e0b9b764091385f7869321bbbbb30e435f7c..90e65373827dc08b0052c52e8e019117d7f82813 100644
--- a/net/quic/spdy_utils.cc
+++ b/net/quic/spdy_utils.cc
@@ -129,6 +129,11 @@ bool SpdyUtils::CopyAndValidateHeaders(const QuicHeaderList& header_list,
     auto iter = headers->find(name);
     if (iter == headers->end()) {
       (*headers)[name] = p.second;
+    } else if (name == "cookie") {
+      // Obeys section 8.1.2.5 in RFC 7540 for cookie reconstruction.
+      headers->ReplaceOrAppendHeader(
+          name, base::StringPrintf("%s; %s", iter->second.as_string().c_str(),
+                                   p.second.c_str()));
     } else {
       // This header had multiple values, so it must be reconstructed.
       string value = base::StringPrintf(